Compile

Compiling is the process of converting a VMF file into a BSP file, so that the game engine can open it. It will also add lighting and visibility optimizations.

How to compile a map
If you see the window pop up, click the Normal button. If you are compiling a map for a Source engine game, you will not see a CSG option.
 * 1) Open the map in Hammer.
 * 2) Click on File, Run/Run Map... or press . If you haven't saved your map yet you will be prompted to.
 * 3) Set all the options to Normal for now. Generally, you shouldn't worry too much about your map's visibility and lighting when you're still creating the layout and gameplay. When you're working with very large maps, VIS and RAD can take a very long time to complete.