What is Paintball?-
Well paintball is pretty simple in some forms. There are many different ways to play paintball. Some of these ways are capture the flag, speed ball and in general Recreation.

In paintball you use a co2, nitrogen or natural air powered gun. Different guns do different things. For a example a Tiger Shark(pump marker made by brass eagle) you can only shoot one ball per pump, a Piranha(semi-auto marker made by PMI) you can shoot only as fast as you can pull the trigger, a EM1(a electronic, seper-semi marker made by Kingman USA) you have different modes of fire 3&6 ball blasts and full auto which can shoot up to 20 BPS(balls per second). There is one problem with some electronic markers. Some chop paint for mainly 2 reasons. One is that there is not a ball detent which stops 2 balls from loading at once. The other is that gravity is too slow to feed the balls into the gun as fast as it is firing, which may then cause only part of the ball to be hit by the bolt.

The "energy" that you may use may also depend on the gun. CO2 was first used in 12 gram cartridges when the first games started around 1982. We still now do use C02 but paintball is being taken over by storm with nitrogen and compressed air. Nitrogen and Compressed Air is now being used to accommodate todays ultra fast firing guns. Those guns need Nitrogen or Compressed Air because CO2 can not be put under very high pressure and because CO2 is much more unstable. Some advantages of using Nitrogen or Compressed Air are that there is no need for a expansion chamber becuase it does not have a liquid to gas transformation stage. Probally the most important is that it does not damage the electronics on some of the new electro guns. Nitro or Compressed Air is also lighter for the more shots that you are getting, for example a 110ci 4500 psi tank would give u approx 1000-1500 shots.

Ok what many people ask "Does it hurt". There are a couple of factors. I find that some paintballs are harder than others.
For example I find that marblizer(pmi-rp shere) is one of the hardest paintballs on the market although they are exceptionally well made. Where as 32 degrees and brass eagle are softer paintballs. I normally use PMI Premium paintballs because they are made well(unlike brass eagle) and are cheap - for a 2000 round case. The other factor is with out a doubt veloicty. Paintball's speed are measured in fps(feet per second) most feilds will not allow the fps over 250. Anything over 320-350fps can break bone. My reccomendation Get A Chrono(+) just to be safe. Back to the question does it hurt well it stings at first and later on u will get a welt and possibly a bruse. The closer some one is to u when they shoot u the harder it will hit. So i leave it up to u to decide weather not it hurts.

Reccomendation-
Wear 2 layers of clothing with no buttons or zippers. Or if u are lucky enough to have the protective equiptment USE IT(shinguards,chest protectors,sock hats,knee pads,elbow pads). AT ALL TIMES WHILE PLAYING PAINTBALL OR ANY ONE IN RANGE MUST BE WEARING GOGGLES OR IF APPROATE A BARREL PLUG TOO.