I've kind of imagined this ( i saw a lot of teen movies
)although I cannot see the purpose of such fraternity. Based on what..../
Well joining one is a huuuuuge process. Every school runs it a little differently, but basically if you choose to "rush", first you go around to all the different houses at your school and talk to the current members. Each house has their own critera, and they each have their own reputation. I am not that knowledgable about frats but I can say at least at SU, Tri-Delt (Delta Delta Delta) are considered like... perfect girls. They require grades above a certain level, you have to be pretty, etc. Other sororities like lets say Gamma Phi Beta or especially Kappa Kappa Gamma have party girl reputations. Basically you go around and interview and have to do stupid activities and the houses decide if they like you or not. There are usually several different rounds and eventually some houses keep wanting you back while others don't. Then in the end, you might be asked to join one, and then a whole new process begins where they torture you and make you do all sorts of ridiculous things to be their friend.
It is paying for friends
A lot of sorority girls will tell you about all the bake sales they have for charities and whatnot, and that they joined to do good for the world, but... basically it's just to find a whole bunch of people just like you to party with
Phi Sigma Sigma was the fat girl sorority at Syracuse
"Phi Piggy Piggy" frats called it
they each have a "type"