Although very similar to paintball in concept and gameplay, airsoft pellets do not leave visible markings on their target and hits are not always apparent. Though the pellets leave bruises or welts on exposed skin (protective gear recommended), the game relies heavily on an honor system in which players who have been hit are expected to call themselves out by shouting "HIT".
The airsoft guns used are mostly magazine-fed, with some having manual/battery-powered spring-piston pump power plants similar to Nerf Blasters, or pneumatically powered by replaceable compressed gas (e.g. propane ("green gas"), 1,1,1,2-tetrafluoroethane or CO2) canisters. Many airsoft guns also have mounting platforms compatible with genuine firearm accessories, and cosmetically more resembling real firearms. This makes them popular for military simulation and historical reenactments. There are also professional gun safety and weapon manipulation training conducted with airsoft in some fields, such as law enforcement training, due to better safety and lower cost.