What is the difference between college and university
It depends where you live.
In the US, people will say "school," "college," and "university," to mean the same place. Here, a college is for a specific program of study, and a university may have more than one college under it - the college of arts and sciences, the college of engineering, etc. You can have a college for advanced degrees, like law and medicine, so it is not linked to the degree you obtain either.
I will let other people explain what a college is where they live.
(I have insulted people from other countries by asking them if they are "in school" - which in the US, could be anything up to a Ph.D. or medical degree - and found that they thought I meant still in high school.)