There's a bunch of large art installations but mostly Coachella is about the "experience." Meet new people, try new things, listen to some new artists you never considered - ultimately it's whatever you make it!
VIP gets you into the VIP areas at the festival where they have better food and booze options. They also accept credit card there and have nicer bathrooms.
The best parties will be in the campgrounds so hopefully you're camping! Just find a party and as long as you have a cool attitude people will be welcoming. Gifts help though.