Wikipedia describes Paintball as
a sport in which players compete, in teams or individually, to eliminate opponents by tagging them with capsules containing water soluble dye and gelatin shell outside (referred to as paintballs) propelled from a device called a paintball marker (commonly referred to as a paintball gun).
I must personally advocate that, while this definition is broadly correct, does not capture the pure essence of Paintball; Inflictin pain, unendurable pain upon your fellow men (or women). While not the most important part, it is surely the most immediately enjoyable part of this otherwise noble sport.
Mostly the game is played outdoors, but you can also find indoor arenas equipped for the enjoyment of speedball match; Indoor or outdoor, however, the pain is still present.
To avoid the foreboding feeling of pain, or better yet, to try to avoid the omnipresent pain in this game, players are allowed, if their coscience allows them, to wear protective, padded clothing. This is advisable on a practical level; when hit you lose only your honour and, ultimately, the match, instead of pints of your precious blood.
You see, you might think I am exaggerating, but I’m not. A single ball comes out of a paintball marker at an average speed of 300 ft/s (90m/s), and (assuming a steady feed of bullets) a marker can spew about 300 bullets per minute of continuous fire. Luckily, being the direct target of continuous fire for a full minute is a statistical impossibility; more probably you’ll be the targeted for a few, bullet-ridden seconds.
Hey, you know what else flies around at 90 m/s? objects caught in the wind of a 3F Class Wind, a Severe Tornado on the Fujita Wind speed Scale. Go figure.
So of course you’ll be trying to avoid these small pellet of edible goo that are being hurled at your face, like, right now. And since in paintball stillness is death, you’ll be running and jumping and dodging and spraining your limbs, stretching your muscles, falling on your soft parts and eating dirt and shit. Quite literally, if you’re playing outside.
But the funny thing is, while you’re avoiding speed based threat by subjecting yourself to movement based threats, you’re carrying if not hugging a small tank of CO2 pressurized enough to tear an arm away. And you’re running, diving and stuff.