Some say a cow has 4 stomachs. Some say a cow has 1 stomach with 4 different compartments. It's all how you look at it.
Either way, it's not like a human stomach.
If this nerd's memory serves, it is an arrangement that allows cows to do something humans cannot: digest the cellulose in grass and break it down into molecules they can digest. Cool intestinal bacteria are involved!
ventre = abdomene, l'extérieur = belly, tummy, gut.
estomac = The internal organ, stomach.