[spijdar]

As a US-ian who is surface level familiar with some non-US education, here in the US "college" and "university" tend to refer to the same thing, which is post-highschool education. Essentially, any higher-education that you aren't required to take, and likewise, have to pay for.

(Edit: for fellow US-ians, I'm vaguely aware that in some non-US places, "college" refers to something we'd either call highschool or in-between highschool and college)

College is (generally) divided into two categories, undergraduate, and graduate education. Undergrad constitutes broad and shallow education with an emphasis on a particular subject. Graduate education is much more in-depth and more selective of potential students.

I believe it's technically possibly to skip the undergrad phase and skip to getting a master's or doctorate degree, but almost never happens in practice. The hierarchy, both for higher education and the job market, expects you to have all of your "lower level" degrees, in spite of your actual abilities.

Even if you drop out of highschool and have a college degree, some jobs will still require you to get a highschool diploma substitute.