What is Airsoft?
The official description from Wikipedia is:
Airsoft is a competitive team shooting sport in which participants eliminate opposing players with spherical plastic projectiles launched via replica air weapons called airsoft guns.
Although very similar to paintball in concept and gameplay, airsoft pellets do not typically leave visible markings on their target, and hits are not always apparent. Though the pellets can sometimes leave red contusions or "welts" on exposed skin, the game relies heavily on an honor system in which the person who has been hit is ethically responsible for calling themselves out.
Airsoft is awesome.