I'm new and just wanted to know what rooting means and what it can do?
Before you think about that you should learn all the ins and outs of your stock phone. Without being fully acquainted with what you have you won't appreciate a Rom.
Rooting will allow you to eliminate the bloat and load custom roms.
The stock Thunderbolt is amazing and will keep you busy for some time.
Welcome! Glad you like your TB and joined us. Here is a link New To Android?!? Check This Out! that will help. I suggest that you read as many different threads on rooting, make notes, and if you still have questions post them. Check out the TB section in the Forum as well.
Forgive your enemies it messes with their minds!