Japan fans are the most general. Otakus focus on Japanese media or for more definitions, see Nobita's video here.
For weeaboos, which is an insulting (but sometimes cocky) term for otaku or anyone passionate of Japan. The definitive example is Logan Paul.
Any additional details are welcome readers.
I came here to explain...turns out to a thread which is givin' information lol
Otaku is the gateway to becoming a weeb, the alcoholic and sometimes toxic version of Otaku.
Otaku is defined as an obsession with a particular subject.
It is not limited to media or anime.
One can be an otaku of woodworking, glassmaking, or language studies.
Math can have otakus.
Science has otakus.
Music has an otaku audience.
But to be a weeaboo specifically refers to a non-Japanese person who values fictional stereotypes of the culture while ignoring and blatantly disrespecting the real Japanese people as well as their own native heritage.