The major difference between blowback and non-blowback Airsoft pistol products is that a blowback pistol's slide moves back and forth with each trigger pull, whereas non-blowback pistols have a slide that does not cycle when the trigger is activated. Non-blowback pistols use less gas, fire more rounds and do not make as much noise as blowback pistols. Blowback pistols are more similar to real pistols in look and feel.
Blowback pistols are intentionally designed to act more like real weapons. The slide must be pulled back to ready the pistol. The slide also remains in the pulled-back position when the air pistol is out of projectiles. The major disadvantage to a blowback pistol is that it uses more gas to fire one round.
Non-blowback pistols are lighter to operate and fire more rounds per minute. These varieties also use less gas which means the air pistol lasts longer between gas refills. Non-blowback pistols are quieter because the slide does not move back and forth.
Both types of pistols use pressurized gas to shoot BB projectiles. Either green gas or carbon dioxide powers Airsoft guns. Pistols made to shoot with green gas can only use that type of propellant, and the same is true of carbon dioxide pistols.