I actually just traded for some of these, and my understanding is that they are clove polyps which is the same thing everybody else said, just thought you might like to hear it for the 15th time, I guess..
You should put a couple pieces of rubble around it and in 6 months or so you will have several frags you could trade out or spread to other parts of the tank.
When my lights come on I will post a picture of mine.
Good Luck!