Pressure in a paintball marker is usually referring to the tank, or the gun itself. Only HPA tanks come in variable pressures (3000-4500-5000 psi). The other pressure is controlled by a regulator, which is the operating pressure (150~200 psi) which is the pressure kept needed to fire and re-cock the gun.
A paintball marker is a paintball gun. It is just called a marker instead of a gun.
Unless you have certain Angel models, High pressure air is fine.
On a paintball gun C02, or High pressure air is necessary. It is compressed air that, when the trigger is pulled and the marker fires, propels the paintball out of the barrel.
type of paintball marker
The owning and operation of a paintball marker does not require any permits.
type of paintball marker
Usually LPR's are used to save on gas usage and if your paintball marker can work with lower pressures (otherwise you may end up with an effect that is similar to "passing gas" where the gas just leaks out of your marker upon actuating the bolt - if your paintball marker requires your air tank to be using a higher pressure)
Yes
yes
No, All DP markers only run on High Pressure Air.
This is totally an opinion question. A mechanical marker is nice because there is no need for batterys and it is truly a bit of paintball history. Electronic markers are great because they are faster, allow more modes, and are the future of paintball.
Ok, considering the last person didn't give you a good answer, here's mine. The paintball "marker" is the proper term for the gun. It's called a marker because it "marks" what it shoots.