One of the biggest differences between a college and a university is size. Colleges are usually smaller than universities and have smaller classroom sizes. Universities are larger institutions that are focused on research in addition to teaching, often offering more advanced master's or doctoral programs than colleges.
Certain universities are made up of several different colleges within the same institution. For instance, a university can have a college of architecture, a college of liberal arts, a college of engineering and a college of fine arts within it. Of course, there are similarities, as both colleges and universities are institutions of higher learning.