A radiant heating system where an element is heated to incandescence by electric current; occasionally coupled with a fan to directly produce hot air as well.
Space heaters are convenient for warming rapidly small places; they are occasionally used as a temporary source of heat while, for example, an oil-burning furnace heats up. They are also rather dangerous; the infrared radiation can set things on fire from a distance, and if they tip over they can easily ignite flammable material.
When purchasing one, prefer a type that has a protected filament and a stable shape.