A womb is the organ in which female mammals grow and carry a fetus before it's ready to be born. Your first home was a womb, but good luck trying to return there.
Womb is a slightly more casual, everyday way to say uterus. Whichever word you use, it's the name of the organ that biologically female mammals have for growing fetuses before birth. Many animals have two wombs, but humans just have one. In Old English, womb meant "uterus," but it also meant "belly, bowels, or heart."