The stomach is a sack like structure surrounded by several muscles.
The wall of the stomach is also lined with mucus. The mucus helps in protecting the stomach wall from the acid.
It helps in the storage and digestion of food,
Both mechanical and chemical digestion takes place in the stomach.
The stomach wall secretes GASTRIC JUICE. This juice contains the enzyme PEPSIN.  Pepsin digests proteins into peptones.
The stomach also produces Hydrochloric acid, which makes the food in the stomach acidic.