What is forgiveness?

Ever wonder what forgiveness really means? I know that it's one of the keys to healing from the abuse that we've suffered. I believe that I've forgiven my abusers, yet, I also know there's a great deal of anger, hurt, shame, feelings of betrayal, etc. still there. So, I don't know if I've truly let it go and forgiven them completely. Any comments you would have on it would be greatly appreciated.