Until recently I assume they were synonymous 😅, Here you go to Uni immediatly after finishing HS.
In the US, a University is usually a collection of colleges. Each college has a somewhat independent structure from other colleges within the University, and each is led by its own Dean. Each college has different requirements of entry and provide rules for what it takes to get a degree from that college. But ultimately, you get a degree from something like “The University of Whatever, College of Engineering”. All the colleges have some certain amount of oversight and guidelines set up by the overall institution.
It can get confusing though because a lot of places that are universities still call themselves “____ College” due to tradition
at least at my university, the colleges consist of departments that are generally similar and are part of similar disciplines, then the department will have a list of degrees to choose from.
So for example at my university we have the College of Business & Economics, which consists of these departments: Accounting, Decision Sciences, Economics, Finance and Marketing, Management, Master of Business Administration, and Executive Education. And then if you for example check out the Accounting Department, they offer the Bachelor of Arts in Accounting, the Bachelor of Arts in Accounting/Economics, and then a Bachelor of Science in Accounting.
For your example, the math department here offers a bunch of degrees I won’t list, and then they’re part of the College of Science & Engineering.