First off, I would suggest talking to people who have been in sororoties. These types of things can help people in many different ways. Also, you don't need to worry about it that much right now, since Rush Week doesn't start the second school starts.
Rush Week is when sororities and fraternities invite freshman to the houses and educate them on the missions and etc. of each house. This is when you'll find out enough information first hand on whether or not you want to join one and if so, which one is right for you.