It’s called “queening”
The female cat—technically, a queen cat—is quite capable of giving birth all by herself, as is true of most animals. Normally she seeks out a dark, secluded place with adequate warmth. The kittens may arrive headfirst or “breech birth”—either is perfectly fine. The mother severs the umbilical cords with her teeth. The kittens arrive one at a time, not all at once, and there are cases when the mother ceases labor, moves the kittens who have already been born to a new spot, then recommences labor in that spot. It’s possible that the kittens in a litter can be born hours apart—or even days.