Well, there's universities and community colleges, which are different. But there are also colleges INSIDE the universities.
I went to Arizona State University, which is a big school (~50,000 students) all studying different things. I specifically studied engineering, which meant I was in the "Ira A. Fulton School of Engineering". (Ira Fulton being some moneybags who made a donation). But many of the different specialties are referred to as colleges. The College of Fine Arts, College of Law, etc. The term college and school seem to be used interchangeably to refer to a specialty within the University (So named for it's universal coverage of educational topics).
Just to add even more confusion to you dirty foreigners.