Difference between grass and hay

Alfalfa is a type of hay.. but is richer than say local or timothy. It's really good for putting on weight fast

Alfalfa is a type of leguminous plant that is made into hay. It can also be used as a green feed not just hay.

The difference between alfalfa and hay is: hay is grass that has been cut and dried, alfalfa is green (not dried) alfalfa hayis the plant cut and dried.