An incandescent light bulb has a small thin wire with two bigger wires holding it up. This wire is called a filament. The filament is the part of the light bulb that produces light.
Filaments in incandescent light bulbs are made of tungsten. Whenever n electric current goes through the filament, the filament glows. It may also be known as the electron emitting element in a vacuum tube. To make the bulb produce more light, the filament is usually made of coils of fine wire, also known as the coiled coil.