What even is booktok?

I always see people talk about it, but I figured it's just the type of women who only read romance books or even guys too who skim through pages and don't actually care about reading etc.

I never see them discuss other genres like horror or scifi, it's always the same types of books with the same covers that get overhyped (if ykwim). I have nothing against romance books when they're done right, but what actually is booktok?