What kind of floor is under this carpet?

So I just bought a house and my first project is to rip up the badly pet stained carpet downstairs. I was expecting like a poured concrete, but it looks lile some kind of tile? This is in the basement of a house built in the mid 60s. I was considering an epoxy floor over the concrete, but now im unsure. The carpet isnt glued down anywhere that ive checked so far. Thanks for any help!

Floor https://imgur.com/gallery/Ptg5z

EDIT: Thanks for all the quick responses! A couple of follow up questions. Its really hard, amd sounds like a stone or concrete when i tap on ot, does that make a diffierence? And assuming its level throughout, is it feasible to install something on top of it rather than remove it, like a vinyl or a laminate?