Nowadays the two terms are often used interchangeably. But the
difference is defined in My2sense's #2 meaning for college:
A school, sometimes but not always a university, offering special instruction in professional or technical subjects.
Colleges are usually smaller in size and offer specific programs in
engineering, music, business, etc. Universitites, on the other
hand, are much larger in size and offer a whole gamut of curriculum
choices.
Sometimes you can have colleges within a university...Esther Boyer College of Music at Temple University for example.