Until recently I assume they were synonymous 😅, Here you go to Uni immediatly after finishing HS.
In Australia “college” can mean two different things.
It can be another word for high school, especially for exclusive, elite private schools. (For example: Brisbane Boys’ College.)
It can be a term for a particular type of residence within a university, especially one that provides more than just a room, but also meals and social activities. (For example, Emmanuel College UQ.)
Historically, it also had at least one other meaning. Among boomer teachers I know, I’ve heard talk of having gone to “teacher’s college”. So I think it used to be a sort of more specialised educational institution with a narrower focus than a university. But these don’t exist anymore, to my knowledge.