Monsterclip is if you're making a quake 2 single player level and you have monsters. What a monster clip would do is act as an invisible wall for that monster, making it so he can't go past it.
Solid is self explanitory. It makes the brush solid so you can run into it, jump on it, etc.
I don't remember the rest of the "confusing" properties off the top of my head. From what I know though, you probably won't need any of them for mapping for paintball.
