Electric frying pans are frying pans whose heat source comes from an electrical element attached to them. They are not designed for stove-top use.
They tend to be square. Almost all come with a thermostat to regulate the heat that you take off when you wash the pans.
Older ones had hot and cold spots, because the heating element was just a ring under the bottom.
Some come with high-domed lids so that you can do roasting or baking in them. For baking, put a metal trivet in them, and then your baking pan on top of that.
Lids usually have a vent in them that you can open to let steam out.
Some come with ceramic inserts, letting them act somewhat like a slow-cooker.
Electric frying pans are good for simmering and slow cooking, both being cooking methods that allow unattended cooking (for short times, for obvious safety reasons.) Electric frying pans will maintain a controlled temperature during this time. They can also be used for braising, stewing, and some oven-type dishes. You can make spaghetti sauce and fried chicken in them.
Electric frying pans are also a popular table tool at parties for keeping food such as Swedish meatballs warm.