I'm not an expert (or libertarian), but my understanding is that a libertarian is basically interested in small government/low government oversight. That platform is a little on both ends of the US political spectrum. They would support more right leaning initiatives like low taxation, free market capitalism, deregulation, but also possibly some left leaning initiatives like legalized marijuana, and generally be against regulation on abortions, gender affirming care, etc.

That's just in theory. Many people use the term when they don't fully embody it's values. I have heard people self identify as libertarian while basically being far right (to be fair, 2016 trump did appeal to anti-establishment voters which includes libertarians). It can also be used incorrectly to mean "right wing voter who doesn't like trump so doesn't want to be called Republican/fascist but still supports many conservative ideologies".

I don't have much insight into other country libertarian parties, other than I believe it is considered fairly centrist in most cases.