Mental Floss: "In America, few people use the phrase 'going off to university,' or “headed to university,” even if they are indeed about to set off for, say, Harvard University. Why did college become the predominant term for postsecondary education? And is there any difference between the two institutions? While university appears to be the older of the two terms, dating as far back as the 13th century, schools and students in North America have embraced college to describe most places of higher learning. There is no rigid definition of the words, but there are some general attributes for each."
"A college is typically a four-year school that offers undergraduate degrees like an associate or a bachelor’s. (Community colleges are often two-year schools.) They don’t typically offer master’s or doctorates, and the size of their student body is typically the smaller of the two. Universities, on the other hand, tend to offer both undergraduate and graduate programs leading to advanced degrees for a larger group of students. They can also be comprised of several schools—referred to as colleges—under their umbrella."
"Some colleges can be bigger than universities, some might offer master’s degrees, and so on. To complicate matters further, an institution that fits the criteria of a university might choose to call itself a college. Both Dartmouth College and Boston College qualify as universities but use the college label owing to tradition. Schools may begin as colleges, grow into universities, but retain the original name ... Keep in mind that some states, like New Jersey, have rules about how institutions label themselves. There, a university has to have at least three fields of graduate study leading to advanced degrees."