The stomach digests food partly by the mechanical means of churning it and partly by chemical means. Proteins are a primary target of the stomach's digestive juices. The stomach's contents are very acidic (hydrochloric acid with a pH between 1-2) and the enzyme pepsin. This is valuable both for breaking food down and for killing microorganisms that come in with the food.

Apart from churning, the stomach performs other functions as well. Like for example stomach is also a temporary storage place of ingested food. It allows the direct passage of substances like as alcohol and some drugs for circulation. The material that leaves the stomach is a mixture of food and digestive juices called chyme which is regulated by circular or "spincter" muscle.