At what point does something become a "fetish"?

Is it literally anything that is not directly related to the act of sexual intercourse? I really don't know what to think because I both don't have any experience in the entire field and I wouldn't ever think of something like liking blowjobs being a fetish. Its even harder for me to understand when it comes to things like gay/lesbian couples where "traditional" sexual intercourse is outright impossible. I cant tell if there's a vague cutoff of something being or not being a fetish, or if its just that some fetishes are so "normal" that we as a whole don't even think of them as such