If you're into airsoft, it is important to know how the guns function. If you're not into airsoft, this is just another thing that is good to know.
Like any advanced device (anything beyond the six simple machines or the advanced machines that come from simply combining a few of the six simple ones), airsoft guns are uniquely designed and, in some instances, are quite complex. There are three types of airsoft guns; spring, electric, and gas. The types refer to the mechanism used for firing airsoft ammunition, which happen to be 6mm or 8mm small, spherical pellets. In most cases, the pellets are plastic, but 6mm paintballs can be used as well.
Airsoft guns differ from paintball guns mostly in their appearance. Airsoft guns are made to be replicas of real guns, so that the game has a more militaristic feel. Also, airsoft guns can be powered in numerous ways, while paintball is basically limited only to various gases (even airsoft guns can be powered with more gases than paintball).
As stated, there are three types of airsoft guns; each one will be gone over briefly (individual types will be gone over in-depth in their own article). The first is spring. Spring guns cannot be automatic nor semi-automatic, as you need to cock (achieved by pulling back the slide on pistols, or pulling the grip on a shotgun) the gun for each shot. As the name says, springs are used to propel the plastic pellet out through the muzzle. To recap, first the user must cock the gun, activating the spring, and then pull the trigger, which releases the spring and shoots out the pellet. The means of firing for this type of airsoft gun are relatively simple, as you can see.
Electric airsoft guns, also known as AEGs (for airsoft electric guns, or automatic electric guns), also use springs as the method of propulsion. However, a battery powers the spring, which enables AEGs to be automatic or semi-automatic. Another bonus is that AEGs are usually more powerful than spring, and although there are several spring guns available that shoot at a higher velocity (but those are expensive spring guns versus cheap AEGs), electric guns are widely believed to be superior.
Finally, there are gas airsoft guns. These kinds of airsoft guns use pressurized gas as the means of propulsion. There are several different kinds of gas used, the most popular being green gas, although carbon dioxide, nitrogen, and high-pressure air can be used. Like AEGs, gas guns are capable of both automatic and semi-automatic fire. When using a gas airsoft gun, the velocities can be adjusted, which can be very useful in some situations.
As a means of being fed ammunition, magazines are used most of the time. For some magazines (hi-cap magazines), it is necessary to cycle a mechanism on the bottom of the clip in order to help feed the airsoft gun with pellets. However, with the other types of magazines, it is not necessary to do this.