A marker, commonly referred to as a paintball gun, is used -- with the addition of a propellant -- to shoot paintballs. When the paintball impacts something it will burst open spraying it's non-toxic paint filling, thus "marking."
Paintball Markers can range in price from $49-1900 due to how some are much better than others, or "high end", as players call it. You usually want to judge a marker by a couple attributes; speed (shooting more paintballs in a short amount of time), durability, weight, accuracy, air compatability ( If you have only a CO2 tank then you wouldn't get a marker that can't use CO2), look (you wanna look cool don't you?), and customability (able to apply useful upgrades). The high end markers contain more of these attributes than low end ones which is why they're more expensive.<p>==Mechanical==
With the passage of time paintball guns have improvised. An example of its latest development is Electronic Paintball Gun. These are advanced and high featured guns that are composed of LCD panels and programmable chips. With all these features they are bound to be expensive.
The stacked tube style is fairly self explanatory, consisting of two tubes--one sitting on the other and welded together, with enough material removed on the back end of the tube to allow the bolt and striker to be connected.
The parts that make up the stacked tube blowback are the body, trigger sear, bolt, striker/hammer, valve, valve pin, cup seal, main spring, and valve spring.
When cocked, in the bottom tube, the main spring exerts forward pressure on the striker, which in turn is held in place by the trigger sear, the valve spring exerts backwards pressure on the valve pin which closes the valve with the cup seal, thus holding back the air/CO2. In the top tube sits the bolt which is connected by a rod to the striker and the paintball which sits in the chamber held in place by a detent.
When the trigger is pulled the sear releases the striker, which flies forward being pushed by the main spring. When it reaches its forward limit of travel it impacts the valve spring, thus pushing back the cupseal and opening the valve. The air/CO2 is released, part of its volume is sent upwards into the bolt, which by this time has pushed the paintball into the barrel. This volume propels the paintball through the air. The remainder of the gas pressure forces itself against the striker, pushing it against the mainspring and all the way back past the sear resetting the striker to its resting position, at the same time the valve spring pushes the pin and cupseal forward closing off the valve and resetting the system for its next shot.
The trigger sear can be released by either mechanical force, in so-called mechanical markers, or by an electro-magnetic solenoid in electronic markers.