The animals every time cannot get food whenever they are hungry instead they need to store the food whenever it is available to them. So, some animals like cows swallow a large amount of food at once and it gets stored in a different part of stomach known as rumen. Here the food is stored as well as partially digested. Now this swallowed, stored and partially digested food is known as cud which returns to mouth for chewing. The animals having this practice are known as ruminants and the process is known as rumination.