Airsoft is a hobby or sport which uses replica firearms to shoot small six millimeter diameter plastic pellets. Airsoft is competitive gaming (similar to paintball), military simulations, target shooting, military training, and recreation. Airsoft guns use lightweight plastic projectiles (BBs) 6mm in diameter instead of metallic 4,5mm BBs. Airsoft guns also typically have a muzzle velocity of less than 180 m/s (600 ft/s). The combination of the lighter BB projectile and the reduced muzzle velocity means that airsoft is generally considered safe when used in a controlled environment and with safety equipment like protective eyewear.

Airsoft games vary greatly in style and composition depending on location, budget, and the quantity of participants. However, they often range from short-term skirmishes and organized scenarios to military simulations and historical reenactments. Gaming with combat situations on a mock battlefield mainly involve the use of common military tactics to achieve the set objectives. Participants typically use varying types of airsoft weaponry along with either real or replica military gear and uniforms.

Skirmishes are also known as "pickup games". This is a more common form of airsoft. These games are considerably less strict with their rules and restrictions, and thus it is the style of play for most players and a common event even for MilSim players. Realism may be broken in this style of play with things like high-capacity magazines, clothing that doesn't match with any nation's uniform (or non-military style dress). Occasionally, teams may use specific uniforms on either side, but usually players dress in a variety of military or paramilitary clothing to their liking.

Skirmishes are often structured as multiple short to medium length games, containing various different scenarios, including capture the flag, attrition style games, deathmatches, or simplified CQB games. Other skirmishes can run for the entirety of the game day, playing out like a much shorter MilSim event, including full game plans with objectives. These objectives can range from anything as simple as capturing a certain location to something as complex as collecting parts of a bomb from around the skirmish site, assembling them, and then planting the assembled bomb in the enemy force's base.