for further wtf is clathrin, when a cell needs to make a bubble - a vesicle - for a certain purpose, like it wants stuff outside of itself to come in or vice versa, clathrin is a little twirly-three-legs dude that hooks together to help form that bubble by being the 'cage' around it.
for why i like them so much, listen, i don't even know man, i just think it's pleasingly elegant to look at, see attached meme for more information