Quote: "I'm guessing that a lightmapper is used to create static lighting effects on a scene so that it does not have to be calculated on the fly. Am I right?"
Yeah, basically it creates the shadows for objects based on where the light you position is.
Quote: "
Once I have my lightmap, how do I apply it in DB Pro? Does it replace my textures, sit over the top of them...I just don't know"
This is the toughy, you SHOULD be able to multitexture your objects with the normal textures and the new lightmap texture but the 2 textures use 2 different UV coordinates which makes this impossible until U6 (where it's fixed, I hear). You can either somehow export a .DBO object with the 2 different UV maps and textures depending on how you made the lightmap in the first place, or use a work-around that other forum members do and create 2 objects, one lightmapped and the other normal textured and then ghost the lightmapped object.
Quote: "Is this process similar to baking textures in a 3D modeller?"
Yep.
"Computers are useless they can only give you answers."