Animation on scroll. How to create such animations?

Question

css

Hello. I am tormented by the issue with animation (examples below), I just can’t find it on the Internet, maybe I’m looking for it wrong. It’s not clear to me how it all works, I looked at the js code, I barely understood something, it was not all clear. Maybe there is a manual, well, like an algorithm for creating such animations.
1. Animation when scrolling. It seems that the site will not scroll, but in fact everything happens when the page is scrolled.
andrikanich.guru/freelance/2017/hranipex - the second block, also the "WIDE
FEATURES" block
2. And I'm also interested in this SVG line, how do you get something like this?
andrikanich.guru/freelance/2019/iliotek/home.html - the third block

Answer 1

1 each - https://scrollmagic.io/
2 each - you can see how it is implemented on the site itself in main.js