Hay is grass and other plants that have been cut, dried and collected. It can then be stored in piles (called hay stacks), or tied into blocks called bales. Bales can be round or box shaped (usually called square bales).
Hay is mostly used to feed animals. Some animals that eat hay are horses, cattle, goats, donkeys, and rabbits. Hay is fed when there is not enough pasture or rangeland on which an animal can graze or they can't graze year round. Farmers and ranchers often need to use hay in the winter when grass is not available.
Hay is different than straw. Hay is made from leafy grass and other plants (such as alfalfa) and is good for feeding animals. Straw comes from the stems of cereal grains, and is not very nutritious. Straw is normally used for bedding to keep animals warm and dry.