A fritter is any kind of food coated in batter and deep fried. Although very similar to a doughnut it differs in the fact that it requires some base ingredient beyond the dough it is cooked with.
In British fish and chip shops, the fish and chips can be accompanied by fritters, which means a food item (such as a slice of potato, a pineapple ring, an apple ring (or chunks) or some mushy peas) fried in batter. Hence: potato fritter, pineapple fritter, apple fritter, pea fritter, etc.
Small cakes made with a primary ingredient, mixed with batter and fried, are found in many American cuisines. “Corn fritters” and “apple fritters” are well known, although the American apple fritter is unlike the British one. Fritters may use regular flour, cornmeal, or a mix. Clam cakes and crab cakes are varieties of fritter.