Can someone explain to me the basic different kinds of weed?

My friend always asks me what kind of weed i want, and I don't know how to respond. lol I don't want to look like a dumb.He asks me about kush, purple, dank,endo,etc. I don't mean the variations of names (like maui wowee), but just the basic outline of what the different kinds of weed are, Like what's the difference between purple and kush. Or just define the basic types I guess.