Delta Force, what is it?

Having watched quite a few movies involving in one way or another people dying in some sort of war or military action I have heard the term "Delta" quite a few times. What what is it? My understanding was that Delta was the most elite of Air Force SOF's, more technologically advanced than SEALS, Recon or Rangers, the best of the best to say the least. So top secret are they that the DoD refused to talk about them in public. So what is Delta? Is it an Air Force SOF unit or Army as I have heard before? Does it even exist? One of my co-workers was in the Air Force for several years and he says that Delta doesn't exist, at all. Can someone (cough PJ cough) enlighten me here? I am willing to listen, but if you don't tell me what I want to hear you will be sorry!

Ok, so I might have made up the last part, might.

There's nothing mystical about them, they're just a another extension of Special Forces (see Special Forces Operational Detachment--Delta, instead of SFOD-A,B,C). The only difference is that they have higher operational security (OPSEC) than most units and different missions. I've talked with the project creator, and he's very down to earth and respectful, a shining example of a Quiet Professional. So whatever you saw in the movies is probably skewed in a lot of ways.

Maytime is right on with the information he has been given. Everyone else, sorry, but you're way off of the mark. Any deeper information about operations, joint operations and personnel make-up is OPSEC and can't be discussed on an open forum. Sorry, guys.

All incorrect posts have been removed.

Question asked and answered; topic locked.