According to Wikipedia, a crêpe is a very thin type of pancake.
A crêpe is made from a relatively thin batter that is spread across a hot pan or griddle, producing a broad, delicate pancake. Unlike many North American pancakes, classic crêpes typically contain little or no chemical leavening, so they remain flat rather than rising substantially.
Crêpes may be sweet or savory. Sweet versions can contain sugar, fruit, jam, chocolate, or whipped cream. Savory crêpes are often filled with cheese, ham, eggs, vegetables, or meat. In French cuisine, buckwheat versions are commonly called galettes, especially in Brittany, while wheat-flour crêpes are generally associated with sweet preparations.
The terms pancake and crêpe overlap, but they are not always interchangeable in everyday usage. “Pancake” is the broader category: it includes thicker, raised styles as well as thin ones. A crêpe is specifically the thin French style. It is also distinct from an omelet, which is primarily beaten egg, and from a waffle, whose batter is cooked in a patterned iron.