Airsoft guns broken into 3 major catagories:
Spring-Powered: Very simple airsoft design where the user pulls back a handle to load and lock back a spring. Spring tension is released when the trigger is pulled. Very simple, usually the cheapest way to get into airsoft. Prices can range from $5-$150. Mostly maintanance-free because it is commonly cheaper to just replace the whole replica.
AEG (Automatic Electric Gun): Not to be confused with cheap WalMart electric guns, AEGs of high quality usually consist of some or all metal bodies and metal gearboxes. (explain gearboxes later). Most common type of airsoft gun on the fields, quality AEGs can range in price from $100-$1,000+. Fire 6mm bb's at velocities usually from 250 fps (feet per second)-500 fps. Most fields have a limit to 400 fps. They run off rechargable batteries stored inside an open area in the body, usually the stock or handguard.
Gas: The 3rd most common type of airsoft gun are gas guns. They are in two catagories, NBB (Non-BlowBack) and GBB (Gas BlowBack). They funcion off of propellants that are basicly propane with silicone lubricant. Blow back is a realistic function where the gas is also used to force back the slide to reload and add realism to the replica. Price ranges fr...