I know a bit about Delta Force, so I can help you out a little.
It was formed in the seventies as a counter-terrorism taskforce, independent of the rest of the military (hence the name 1st Special Operations Detachment - Delta), although they do work closely with them, as well as the FBI, CIA, Secret Service, NSA, etc.
They take on all kinds of missions - bodyguard, intelligence gathering, recon, undercover work, hostage rescue, basically missions from all walks of the military. Delta Force has the hardest selection process in the world, and operators are constantly being trained intensely when not on active duty.
Delta Force is made up of of three operating squadrons - also known as Sabre Squadrons (A, B, and C) which are composed of smaller units of troops, each specialising in a certain skill (HALO, mountaineering, etc.). Four-man teams are usually the go, and they can form with other teams to form a section.
Their first full operation was a complete disaster mainly due to poor interaction between Delta and the other military components of that particular mission, and as a result the US Special Operations Command (USSOCOM) was formed to manage the co-operation of different special forces of the United States. Apparently Delta has been assigned to a new command since September 11 2001, known as Task Force 11. I don't know much about that though.
Some weapons used by Delta Force:
- Colt M4 Commando is commonly used
- M16A2
- CAR-15 - sort of a variant of the M4
- HK MP5 submachine gun and MP5SD (integrated silencer)
- M249 SAW (light machine gun)
- Browning M2 (heavy machine gun)
- Remington 870 combat shotty
- HK PSG sniper rifle
- M24 sniper rifle
- Barett M82A1 .50 cal heavy sniper rifle
- M203 detachable underslung grenade launcher
- M79 grenade launcher
- Car Gustav
- LAW
- AT-4
- Beretta 92F handgun