useEffect in React — the invisible engine behind real apps

In Part 1 of “Let’s Master React Hooks Together” we focused on useState — how React remembers things, updates UI, and keeps everything in sync. You learned how to control your app. But then comes the next question: What happens when your app needs to talk to the outside world? You open Instagram, blink once… and boom — your feed is alive. Posts load. Stories appear. Notifications sneak in. Everything feels instant. But here’s what most beginners don’t realize: 👉 React didn’t do that. 👉 React o