A cracker is a type of biscuit that developed from military hardtack and nautical ship biscuits.
The holes in crackers are called "docking" holes. The holes are placed in the dough to stop air pockets from forming in the cracker while baking.
The name "cracker" is most often applied to flat biscuits with a savory, salty flavor, in distinction from a "cookie," which may be similar to a "cracker" in appearance and texture, but is sweetened. Crackers may be further distinguished from cookies by the manner in which they are made. Crackers are made from layered dough not unlike puff pastry while cookies are made from a dough similar to cake batter but without a leavening agent. Crackers sometimes have cheese or spices as ingredients, or even chicken stock.
Brands including Captain's Wafers, Club Crackers, Town House Crackers, Ritz Crackers, Cream crackers and Water biscuits are often spread with cheese, pâté, or mousse.
Saltine and oyster crackers are often used in or served with soup.
Mock apple pie is made from Ritz (or similar) crackers.
Graham crackers and digestive biscuits are somewhere between crackers and cookies and were invented with health benefits in mind.