AirSoft guns are BB guns, spring or compressed air fired except some full autos are electric, firing a .20 or .25g biodegradable BB at 350 fps or less. If you are hit, rules of sportsmanship demand that you acknowledge it. The big advantage is that the AirSoft guns are replicas of the handguns, rifles and submachine guns actually used by police and the military. They fit holsters made for the real things. And they are less expensive than paintball guns.
Scenarios are much the same as in paintball and are simulations of military challenges.
In Capture the Flag each team has a flag and the other team tries to capture it and bring it to their own base. Needless to say, safety rules require at lease eye and ear protection, better a full-face shield. It's an attractive frames site with dated news items in the left panel. No dues for now, they expect to impose dues and become a non-profit organization. Nice framed site with a left panel index.