In American English, college and university are generally used interchangeably, but there are some subtle differences between them. University usually denotes a school that offers full undergraduate and graduate programs, while colleges usually offer more narrow programs and may have no graduate studies at all. But there are no official designations for these terms, and colleges and universities can call themselves what they want.
In practical American usage, university has connotations of prestige that college doesn’t have, although there are some highly respected universities that call themselves colleges out of tradition (e.g., Dartmouth College). Still, no one talks about going to university in the U.S. After high school, you go to college, even if the college you’re attending calls itself a university.
For example, these American publications use college as the generic term for higher education and higher-educational institutions:
Another way to keep colleges in decent financial shape during tough economic times, of course, is to raise tuition. [NY Times]
He was the first in his family to go to college. [Wall Street Journal]
Texas students were slightly behind their peers nationwide in performance on college-caliber Advanced Placement exams. [Houston Chronicle]
Some American universities refer to their undergraduate programs as colleges (e.g., Harvard College at Harvard University), while others use college to denote units within the university organization. For example, the University of Michigan has the College of Literature, Science and Arts, the College of Engineering, and the Taubman College of Architecture and Urban Planning, among others.
British, Australian, and Canadian English
In the U.K., universities are institutions that award degrees, while colleges are institutions that prepare students to earn degrees. The system can be rather complicated and varies from school to school. In practical usage, British English speakers generally use university as the generic term for higher education—for example:
She will be the first in her family to go to university. [The Guardian]
In the past a lot of people have gone to university for reasons other than to get a job. [Financial Times]
The same roughly applies in Canada and Australia, where university is used more often than college as the generic term—for example:
It used to almost be an act of rebellion to take a year off between high school and university. [Sydney Morning Herald]
Only 23 per cent of the first generation go to university, by far the lowest rate among any immigrant group. [Globe and Mail]