What is the difference between a college and a school in a university?
"College" and "university" usually mean the same thing; that is, post-secondary education, or education after high school.
However, there can also be the distinction that a college only offers undergraduate degrees (e.g. bachelors), whereas a university offers graduate degrees (e.g. Masters, PhD).
A single university can be divided into "colleges" or "schools", which means they are all a part of the university but focus on a specific subject. They can be considered as departments of a university. For example, the University of Southern California has the College of Letters, Arts, and Sciences; the Viterbi School of Engineering; the Thorton School of Music, the Roski School of Fine Arts; etc. Each has its specific emphasis but they are all on the same campus and all of the students will graduate with a degree from USC.
I hope this helps answer your question!