What is the 1 stomach of a cow and what does it do?

Cows have one stomach with four chambers. Each of those chambers are called the reticulum, the rumen, the omasum and the abomasum. All four of these chambers, by working together, are responsible for the break-down and digestion of feedstuffs that the cow eats so that nutrients and minerals can be absorbed to be used by that cow's bodily systems.