Parties can help you to earn XP, money and you will get 1 point of Fame per each party.
There are 6 types of parties:
You can access Parties from the Wine Glass Icon at the bottom of the page, in the right. Some parties have requirements: you should have a specific number of clique members and a specific hotness; but you can enter at clique members' parties without any requirement (you have a VIP Pass).
To win a party you should put on the highest clothes you have in your closet for the specific type of party (Beach Party, Nightlife etc.) and win 3 Shutdowns.
But you can also throw a Party to win money, XP and Fame points (but you win them if your party reach the number of attendants AND you have to be level 20 to throw a party). You can choise the location, the Party type, the room's appearance, the reward which the party will give and additional details in the room (Dancefloor , Dj , Bouncer , Lounge , Bartender ). Every additional detail increases the number of attendants. But for all of these, you need Fame. The higher the Fame, the higher the rewards.