How do light-bulbs work?

Answer 1

An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation.

Answer 2

The original lightbulb (incandescent) works by electrical currents flowing through normal wires and into a metal wire (filament). A filament wire glows when heated to a high temperature. When the electrical currents transfer enough heat, the lightbulb will produce light. The bulb is to protect the filament from cooling in open air. Filament glows because of it's resistance to heat. Most metals won't reach the point of being so heated it glows, but filament wires are thin and can resist heat enough to emit light.