Base rock is not a "type" of rock. Live rock isn't a "type" of rock.
For example - Fiji, Lalo, Tonga, Melanesian are all type of rocks. Basically they are labeled by where in the world the come from. Different locations, different minerals that make up the rock which forces different shapes, densities which cause diferent about of pourousness (is that a word?).
Base rock is live rock that just isn't as pretty, and doesn't have as much "good" bacteria and good algea growing on it. Base rock is cheaper for these reasons. Eventually it will become live rock will all the good stuff.
Imagine a pile of rocks in the ocean. The stuff on top that gets the most light, therefore the most good stuff growing already, is sold as "premium" live rock. The stuff on the next level is sold as just "live" rock. The stuff on the bottom is sold as "base" rock.
Sorry to be so winded, just couldn't think of a better way to explain it.
You can fill your tank with all live rock, mix of base and live or all base rock.
Most use a mix. The more live you start with the faster the base will transform into live.
You don't have to "acclimate" it, but you typically do need to cure it. Do a search on this site about curing rock, you will get many results and answers.
Good Luck