Lots of people talk about "releasing" the clubhead through impact but oftentimes are confused as to what exactly is happening. While you can certainly have different definitions, clubhead "release" to me describes the action of the lead hand and arm as the club moves through the hitting area.
You can tell alot about how someone's "release" functions just by watching them hanging out on the range talking to a friend. Check out this video that describes what "release" means to me, what to watch out for on the range, and a quick little drill to help you get the right feeling the next time your out on the tee practicing.
I hope this helps you...please comment and let me know your thoughts and questions!