A light bulb was a device that uses an electrical current to produce light. Various types of light bulbs did this in different ways.
On Earth it was invented by Thomas Edison, but seemingly identical technology also existed on other planets, for example Ekos.
In an alternate 1944, Trip Tucker managed to escape Nazi captivity by smashing a light bulb, and using the glas shards to cut the ropes around his wrists. (ENT: "Storm Front, Part II")
Contrary to popular expectation, the Y2K bug did not turn out a single light bulb on new year's eve 2000. (VOY: "11:59")
In 2151, Jonathan Archer complained that you can't just yank out an antimatter injector as if it was merely a light bulb. (ENT: "Acquisition")
In 2268, Spock managed to utilize and Ekosian light bulb and a piece of Rubindium to create a primitive laser. (TOS: "Patterns of Force")
Vic Fontaine once referred to himself as a light bulb, albeit one with "pretty sweet pipes", acknowledging the fact that, as a hologram, he was little more than photons and force fields. Doctor Bashir's friends were surprised that Fontaine was a self-aware hologram, something they had never seen before. (DS9: "His Way")