"Texture name", _tex:

Name of texture to emit light.

"Filter max distance", _frange :

Excludes faces whose centers are far from this light_surface.

"Filter max dist to plane", _fdist :

Same as above, but checking the distance to the whole texture plane (instead of face center).

"Filter entity classname", _fclass :

Same as "Class In Filter" with <unknown> filter type.

"Filter entity name", _fname :

Same as "Name In Filter" with <unknown> filter type.

"Texture brightness", _light  :

The brightness of texture. Works the same way as in light and light_spot.

"Inner(bright) angle(default 90)", _cone :

Like in light_spotlight, custom values used to simulate spotlight.

"Outer(fading) angle(default 90)", _cone2 :

"Adjust emit scale(1.0default)", _scale :

When simulating light_spotlight, this is scale value for light emission.

"Grid size of sampling", _chop :

Grid size of sampling. However lightmap grid cannot be changed. This keyvalue functionality is very limited.

"Dark gap in front of texlight", _texlightgap :

Moves lights out of texture by few units (specified amount or chosen from pre-definied values). It's useful in situations where
light leaking out of the brush in opposite direction of light. Example:

"Fast", _fast :

Determines usage of '-fast' compile parameter for light. Set it to 'Yes' if brightness is low and the face is large.

"Classname in Game", convertto:

Used by compilers. You don't need to set this.

1: "Initially dark": If set, the light will be turned off at map start. This counts as an additional lightstyle. If you have multiple lights
by the same name, they will count as one additional lightstyle, even if some of the lights are initially dark while others are not. Note that there can be at most 4 different light styles affecting a face in your map. Otherwise, light styles will be discarded from it, causing unrealistic lighting in extreme cases.