I'm trying to learn how sites [like this one](https://stripe.com/us/customers) are able to move their images and create animations with code.

I have basic HTML/CSS knowledge, and from looking at their [code](https://imgur.com/a/659boh6), I see that their pixels change continuously. The image below doesn't show that obviously, but I'd like to know how they are able to make it so that their translate pixels are constantly changing? Does it involve a javascript file somewhere? and if so, where is that located?