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Tech & Internet · 200 lessons in the app

How the tech you use every day works

Why your battery percentage jumps around, what the cloud physically is, why two-factor authentication helps so much. Short explanations of the machines in your pocket, with the source for each.

Try 4 lessons exactly as they appear in the app

Tech & Internet40s read

Lesson 1 of 4

Why Your Phone Battery Lies

Lithium-ion batteries do not store a fixed number of percentage points; they store energy. Phones estimate the percentage by reading voltage and comparing to a model that drifts over time. That is why your phone can drop from 30% to 1% in minutes, especially when cold. The cold thickens the battery's internal chemistry and the voltage briefly sags, fooling the gauge.

Source Linden, D. & Reddy, T. (2002). Handbook of Batteries.

Quick quiz

Why might a phone battery suddenly drop from 30% to 1% in cold weather?

Tech & Internet40s read

Lesson 2 of 4

What 'The Cloud' Really Is

The cloud is just other people's computers, in warehouses, with very good air conditioning. Companies like Amazon, Google, and Microsoft build enormous data centres and rent out slices of the hardware by the second. When you save a photo to iCloud or watch a Netflix show, you are using a sliver of someone's industrial server that may be on another continent.

Source Armbrust, M. et al. (2010). A View of Cloud Computing. Communications of the ACM.

Quick quiz

What is the most accurate description of 'the cloud'?

Tech & Internet40s read

Lesson 3 of 4

Why Two-Factor Authentication Helps So Much

Passwords leak constantly through breaches, reuse, and phishing. Two-factor authentication adds a second proof: something you have, like a phone or a hardware key, on top of something you know. Even if your password is stolen, an attacker still cannot log in without that second factor. Studies by major providers show this single step blocks the overwhelming majority of automated account takeovers.

Source Doerfler, P. et al. (2019). Evaluating Login Challenges as a Defense Against Account Takeover.

Quick quiz

Which form of two-factor authentication is generally considered the most resistant to phishing?

Tech & Internet45s read

Lesson 4 of 4

What a Vector Database Is For

A vector database stores embeddings and lets you ask for the items closest to a query in that high-dimensional space. Type a question, embed it, look up the nearest passages from a collection of documents, hand them back to a language model. That pipeline, called retrieval-augmented generation, is how chatbots stay informed about company-specific information without retraining the underlying model.

Source Lewis, P. et al. (2020). Retrieval-Augmented Generation for Knowledge-Intensive NLP Tasks.

Quick quiz

What is the main purpose of a vector database?

196 more tech & internet lessons in the app

Every title here is a lesson in Scroll, with its own quiz. Five a day are free; Premium has no daily limit.

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  1. How the Internet Actually Works
  2. Why HTTPS Matters
  3. What Cookies Really Do
  4. How Wi-Fi Differs From the Internet
  5. How GPS Pinpoints You
  6. Why Captchas Are Getting Harder
  7. How AI Models Learn From Examples
  8. Why USB-C Has One Connector but Many Speeds
  9. How Public-Key Encryption Works
  10. Why Software Has So Many Bugs
  11. How Streaming Video Survives Bad Connections
  12. What an IP Address Reveals
  13. Why Phishing Still Works
  14. How Search Engines Decide What You See
  15. How Push Notifications Reach Your Phone
  16. What Open Source Actually Is
  17. Why Quantum Computers Are Hard to Build
  18. Why GPUs Power Modern AI
  19. Why Closing Apps Can Slow Your Phone Down
  20. Why SSDs Wiped Out Spinning Drives
  21. Why Email Travels Through So Many Strangers
  22. What End-to-End Encryption Actually Means
  23. What a VPN Actually Hides
  24. Why Bluetooth Is Named After a Viking
  25. How Tap-to-Pay Works in Half a Second
  26. Why QR Codes Have Those Weird Squares
  27. Why JPEGs Look Worse Each Time You Save Them
  28. Why Some Languages Are Faster Than Others
  29. What an Operating System Kernel Actually Does
  30. How One App Does Many Things at Once
Show all 196 titles
  1. Why Computers Hide So Many Copies of Things
  2. Why Web Pages Look Slightly Different in Each Browser
  3. What an API Really Is
  4. Why Relational Databases Still Run the World
  5. How a Single Quote Can Break a Website
  6. Why Comment Boxes Are Dangerous
  7. Why the Best Hacks Use No Code at All
  8. Why Ransomware Is So Effective
  9. How a DDoS Attack Drowns a Website
  10. What a Firewall Does, and Doesn't
  11. What Tor and the Dark Web Actually Are
  12. How CDNs Make the Internet Feel Fast
  13. TCP vs UDP: Reliability vs Speed
  14. Latency vs Bandwidth: Why Both Matter
  15. Why 5G Is Less Magical Than the Marketing
  16. Why the Internet Mostly Travels Underwater
  17. What a Container Actually Contains
  18. Why Big Companies Run on Microservices
  19. Why Programmers Argue About Git
  20. Why Software Has 'Tech Debt'
  21. Why Moore's Law Is Slowing Down
  22. What a Transistor Actually Does
  23. Why Only One Company Builds the Best Chip Machines
  24. Why OLED Beats LCD for Black
  25. Why High Refresh Rates Feel So Smooth
  26. Why Audiophiles Argue About Lossless
  27. Why Deepfakes Are Getting Harder to Spot
  28. Why Language Models Hallucinate
  29. What an AI Token Really Is
  30. Why AI Embeds Words as Numbers
  31. Why APIs Have Rate Limits
  32. How a Load Balancer Keeps Sites Up
  33. The 3-2-1 Backup Rule
  34. What a Hash Is, and Why It Helps
  35. Why Salt Goes With Hashed Passwords
  36. What Single Sign-On Saves You
  37. What OAuth Lets You Skip
  38. Why CORS Blocks Your JavaScript
  39. How WebSockets Keep Chats Alive
  40. What Browser Extensions Can See
  41. What a Progressive Web App Is
  42. Why the Internet Ran Out of Addresses
  43. How NAT Quietly Saved IPv4
  44. Why Your Lightbulb Is on the Internet
  45. Why Zero-Day Bugs Are So Valuable
  46. Why Companies Pay Hackers
  47. What a Penetration Test Really Buys
  48. Why Every Letter Has a Number
  49. Why Emoji Are a Standards Body Decision
  50. Why Computers Run on UTC
  51. Why the Y2K Panic Was Mostly Justified
  52. Why Computers Cannot Be Truly Random
  53. Why a JWT Looks Like Three Things Glued Together
  54. How Video Calls Connect You Directly
  55. Why Some Web Apps Work Offline
  56. Why Right to Repair Is a Tech Fight
  57. Why Your Old Phone Got Slower
  58. Why a Mesh Network Has No Centre
  59. What Zero Trust Security Means
  60. Why Code Reviews Save Companies
  61. Why DevOps Was a Cultural Change
  62. Why Standards Bodies Quietly Run the Internet
  63. Why Browsers Cache Some Pages and Not Others
  64. Why Dark Patterns Work So Well
  65. What an A/B Test Actually Measures
  66. Why Banks Still Run on Mainframes
  67. How DNS Poisoning Sends You to a Fake Site
  68. How Browsers Store Your Passwords
  69. Why Password Managers Beat Memory
  70. What Bitcoin Actually Is
  71. Blockchain Without the Hype
  72. What a Smart Contract Really Does
  73. Why Adding People Slows a Late Project
  74. Why Software Looks Like the Org Chart
  75. Agile vs Waterfall in One Page
  76. What Scrum Actually Is
  77. Federated Learning: Train Without Centralising
  78. Can You Watermark AI Output
  79. How AI Generates Images From Noise
  80. Why Multimodal Models Are a Big Deal
  81. Fine-Tuning vs Just Prompting
  82. Why Asking AI to 'Think Step by Step' Helps
  83. Why AI Models Have Guardrails
  84. What an NFT Actually Owns
  85. Why Stablecoins Try Not to Move
  86. Why a Cold Wallet Is Safer Than a Hot One
  87. Mining vs Proof of Stake
  88. Zero-Knowledge Proofs in Plain English
  89. Why AI Voice Cloning Got So Good So Fast
  90. The Joel Test
  91. Why Synthetic Data Is Useful and Risky
  92. Why Kanban Boards Limit Work in Progress
  93. What CI/CD Actually Builds
  94. How Feature Flags Decouple Deploy From Release
  95. Why Canary Releases Save Companies
  96. Blue-Green: Switching Production in One Move
  97. Why Rollbacks Should Be Boring
  98. What a Postmortem Is For
  99. Why Engineers Deliberately Break Their Own Systems
  100. SLOs vs SLAs in Plain English
  101. Why On-Call Rotations Exist
  102. What Incident Response Looks Like in Practice
  103. What a Game Day Is
  104. Disaster Recovery: Planning for the Bad Day
  105. RPO and RTO: How Bad Is Bad
  106. Why Multi-Region Failover Is So Hard
  107. What Edge Computing Actually Solves
  108. Why Serverless Still Uses Servers
  109. Observability vs Monitoring
  110. Logs, Metrics, and Traces: The Three Pillars
  111. How CRDTs Make Real-Time Collaboration Possible
  112. What the CAP Theorem Actually Says
  113. Why 'Eventually Consistent' Is Not a Bug
  114. ACID: The Old Promise of Databases
  115. Why Big Databases Get Sharded
  116. Why Databases Have Replicas
  117. Why Engineers Cache Things in Redis
  118. How Message Queues Decouple Services
  119. What Event-Driven Architecture Means
  120. How Pub/Sub Reaches Many Subscribers At Once
  121. What a Webhook Actually Is
  122. GraphQL vs REST in Practice
  123. Why gRPC Is Faster Than Most REST
  124. What WebAssembly Is For
  125. Why Web Workers Run in the Background
  126. ARM vs x86 in One Page
  127. RISC-V and the Quiet Standards Battle
  128. Why Cables Sometimes Whine on Speakers
  129. What a Faraday Cage Does
  130. How Power Over Ethernet Works
  131. Why Servers Have Their Own Batteries
  132. Why Hot-Swappable Drives Save Time
  133. What RAID Levels Actually Mean
  134. Why Servers Use ECC Memory
  135. How SMART Predicts Drive Failures
  136. Why Apps Pin Their Server's Certificate
  137. Who Decides Which Sites You Trust
  138. How Let's Encrypt Made HTTPS Free
  139. What PKI Is, in One Page
  140. Why SSH Keys Beat Passwords
  141. Why Browsers Sandbox Tabs
  142. Why Privilege Escalation Is the Real Prize
  143. Heap vs Stack: Two Kinds of Memory
  144. How Memory Leaks Sneak Up On You
  145. What a Garbage Collector Does
  146. Reference Counting vs Tracing GC
  147. How Deadlocks Freeze Programs
  148. Why Mutexes Are Just Polite Tokens
  149. What Atomic Operations Get You
  150. Why Big-O Notation Matters
  151. Why Not All Sorting Algorithms Are Equal
  152. What a Hash Table Actually Stores
  153. Why Binary Search Trees Stay Sorted
  154. Why Computer Scientists Care About Graphs
  155. Why Recursion Feels Like Magic
  156. Why the Halting Problem Is Unsolvable
  157. Why Software Licences Matter More Than Code
  158. Why Unix Treats Everything as a File
  159. Why the Terminal Still Matters
  160. Why Regular Expressions Are Both Loved and Feared
  161. Why Time in Software Is Constantly Buggy
  162. Why O(1) Sometimes Loses to O(n)
  163. Why Binary Search Is Worth Memorising
  164. Why Lookup Tables Beat Recomputation
  165. Why Tail Calls Save the Stack
  166. Why 'Stack Overflow' Was Already a CS Joke

About the tech & internet lessons

Do I need a technical background for the tech lessons?

No. Each lesson explains one thing in under 100 words, and the quiz checks the main idea, not jargon.

Do the tech lessons cover AI?

Yes, alongside the internet, phones, security and software. Each AI lesson explains one idea, such as what a vector database is for, with its source.

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