A fraternity is a group of people who share a common profession or interests. There are more types of fraternities than there are sororities. There are fraternities that are based on majors, religion, interests, and like sororities those that have their national governing body the Interfraternity Council (IFC). The IFC ones are the ones that you normally associate with movies.
Depending on the type of fraternity, for example those that have housing arrangements, members can pay upwards of $1,500 per semester. There are smaller ones where the semester fee is significantly smaller.
Bid day is known as the last day of recruitment when potential new members receive a bid (invitation) to join that chapter and become an official new member.
When new members are added to the fraternity they are considered a pledge. This is basically a trial period for those new members to see if they will be initiated. Once they are initiated they will be taught the “secrets” and mottos of the fraternity.
Rush week is a week where potential new member get to meet, tour and chat with the fraternities on campus. During this week, they are able to narrow down their choice of the fraternities they would like to join, and fraternities narrow down the potential new members they would like to take on. There are a series of activities involved during this week that are put on by the fraternities, can vary from formal to informal.