A Lamp (also called a light) is an electronic light source. It is a basic level editor tool, and is used for lighting in custom maps and the Campaign, as well as for cosmetic and decoration uses, namely its ability to create scenic shadows. The lamp is an entity and cannot be shaped, but its parameters can be altered to give it flare and power.
Lamps are often used near the seems of backgrounds and sky to create an environmental lighting effect. They are also somewhat interactive and fragile, and (as of version 1.20) can easily be shattered by swords or guns. A shattered flare lamp will either take on the characteristics of a non-flare lamp (in multiplayer) or remove its lighting effect completely (in singleplayer). Lamps give off a bluish-white glow, though the blue coloring was more intense in the older versions of the game.
Lamps are generally divided into two separate categories, flare and non-flare. By default, a lamp will have flare - meaning it can be seen clearly as an object and will create a spotty effect on the screen. Lamps with flare can also be destroyed. Non-flare lamps give off visible light, but are typically invisible and indestructible objects. They do not appear as conventional lights and cannot be broken. The power of a lamp is also a changeable parameter, with the default power being 0.4. Power determines the intensity of the lighting effect; a lamp with ridiculously high power will likely crash the game.