Compiler Options

Checks for map leaks. No light information is created. Because there are no shadows to get in the way, this mode is also good for looking for z-axis fighting between textures.
All the world is made into a single bsp branch. It's fast, but when you look in a particular direction, you see every single detail in that direction. Nothing is blocked. A light map is created. This mode was used for space maps.
The world is subdivided and broken up into smaller chunks so you can see only what is logically in your view. A light map is created. This is what is used to check polygon-in-view counts. Combined with light extra, it is the final compile for all maps.
When you add or subtract non-brush model entities from a map, use this compiler. It's very quick. If you change a brush model entity (like a trigger or a door), you must do a compile that includes a vis stage (fast or full). Also, if a brush model entity also has a md3 model component, the map must be at least fastvis'd for that entity to appear in the map.
Use only if no geometry has been changed. It will rebuild the light map with the new infomation.
what is says. The map is compiled without curves.
The map is compiled without water, lava, or slime.
No lightmap is generated. A fast way to check polycounts.
-light extra
A finer degree of subdivision is used to create a more detailed lightmap. This is generally only done when the lighting is going through a final fine-tuning because it takes a long time.