How would you use the Intersection Observer API to implement lazy loading, infinite scroll, and impression tracking without scroll event listeners?

Imagine you have a big toy box and you only want to see the toys you're playing with right now. The Intersection Observer is like a helper that tells you when a toy comes into your view, so you can pick it up without having to watch all the time. It helps websites load pictures only when you scroll near them, and it can count how many times you look at things.