Paintball was invented in 1981 by a Wall Street Stock Trader and an Outdoors Man when they got into a debate and decided to use paint guns from a farm catalouge to settle it. They gathered 10 more people and had the first game of Paintball!
For a more indepth read and more indepth info check out the wikipedia article!
The basic gear for Paintball is simple.
-A Paintball Marker
There are 3 different main ways to play Paintball
=Speedball: Flat and open field with manmade obstacles.
=Woodsball: Paintball done outdoors and typically in the woods. natural terrain and defenses.
=Scenario: Paintball with a theme, typically involves LARP (Live Action Role Play).
There is much more that im leaving out but they can be found at the wikipedia link (located in the History of Paintball section