Fun Font question about owning Fonts.

…so there are some fonts that we all use (times, helvetica, Impact…) and some that I think are “the suck” like those FAKE fonts that are meant to look like these fonts but have a different but similar name.
The “good/real” fonts are EXPENSIVE and most of the other ones (fake) are Free.

So here is my question, when you get windows/Mac OS/MS Word/Adobe programs/etc. (basically any app) you get some fonts. Like windows comes with some fonts, and some apps come with fonts also.

Does that mean that I have the right to use those fonts, or do I have to Purchase them from…. ( fonts.com, linotype.com etc.)

Thanks