Incandescent light bulbs produce light when their filament is supplied with an electrical current that heats them up to several thousand degrees Fahrenheit.
The first versions of incandescent light bulbs utilized carbon filaments. Modern incandescent light bulbs utilize tungsten filaments, because out of all known metals, tungsten has the highest melting point, making it ideal for withstanding extreme temperatures.
The light output of a light source is measured in lumens. Incandescent light bulbs are some of the most inefficient light bulbs on the market but they are still capable of producing a respectable 8 to 21 lumens per watt of power drawn.
The earliest versions of incandescent light bulbs contained a vacuum, because air causes a bulb's filament to oxidize at high temperatures. Later, it was discovered that using inert fill gases like argon or a nitrogen-argon mixture will slow the evaporation of filaments.
Incandescent bulbs typically only last for around 750 hours. Tungsten filaments evaporate slowly and unevenly throughout the life of the bulb. Parts of the filament become thinner than other parts of the filament, which often results in the filament eventually snapping, melting or breaking and therefore being unable to illuminate.