They are usually carbon steel pans, up to 35 cm (14 inches) wide, but generally about 18 to 20 cm (7 to 8 inches) wide.
Many people reserve a suitably shaped non-stick frying pan for cooking only crepes in, and call it their crêpe pan. They get it seasoned, and, as only crêpes are ever being cooked in it, there is no need to ever wash it.
The pan should be heated until drops of water on it will dance. Generally you put in about 4 tablespoons (¼ cup / about 50 ml) of batter at a time, then you tilt and rotate the pan about until the entire bottom has a thin coat of the batter. A good crêpe pan should be light enough to raise and tilt easily to cause the batter to spread freely.
You can get electric crêpe pans; there are also uniquely designed ones, such as upside down ones, whose surface you dip into the batter. Commercial electric ones are often just round, flat surfaces with no rims or just slightly upturned edges.
For the record, Julia Child recommended using a non-stick skillet rather than hard-to-care-for specialized crêpe pans.
See also: Crêpes
Associated Press. A Julia Child lesson: Crepe pans. Phoenix, Arizona: The Arizona Republic. 7 August 2009.