The difference between pistols and revolvers are that pistols are typically antiques and will fire only one shot at a time. Revolvers can fire multiple times without having to be reloaded.
Generally, hand gun includes revolvers and pistols. Pistols, refers to semi-automatics
DAK is unknown to me. The other stands for Double Action/Single Action
Features
Some people distinguish between pistols and revolvers. Both are handguns, but revolvers may not be pistols. A pistol would be an automatic, a single shot, a derringer type pistol, etc- but a revolver must have a cylinder holding the cartridges that revolves.
The .45 ACP--which stands for AUTOMATIC COLT PISTOL is used in semiautomatic pistols. The .45 Colt is used in revolvers.
The two paintball pistols are identical except of the materals. One has a composite plastic and the other is all metal. Though they both perform the same.
ACP designates a cartridge desgined by Colt for their pistols- Automatic Colt Pistol. LCP is the name used by Ruger for a model of lightweight compact pistol. LCP
A Beretta is a manufacturer of pistols, rifles and shot guns. Pistol is a term used to describe any type of handgun, but mostly is used for semiautomatics as opposed to revolvers
The FS is the most advanced model of the Beretta 92. I wouldn't recommend the early M9 pistols (which were basically Beretta 92F pistols) over the 92FS, but the later production M9 pistols are 92FS pistols. The main difference being the the actual M9 pistol production is supervised directly by the DoD.
The length of the barrel. Guns/pistols can be held by one hand. While a rifle requires two hands to properly hold it. Both are air powered.
The 22 is a very small bullet and the 38 is about 4 times larger. The pistols however may be about the same size but will be chambered accordingly.