Much like paintball, the rules are very simple: once you get hit once, you are out for the rest of the match. However, it is sometimes difficult to know if you have been hit or not, due to the fact that airsoft guns shoot plastic BBs that leave no visible blotch of paint (which means that you literally have to feel the bb hit you in order to know that you have been shot).
This can sometimes be a problem since it may be hard to feel the BB hit you, bases on certain factors, such as the thickness of your clothes, or the distance the airsoft BB was shot from and so on.
As far as the weapons used for airsoft battles, there are many, MANY options available (far more than with paintball). The most popular type of airsoft gun is the AEG, which stands for automatic electric gun. This particular airsoft gun is fully automatic and uses a battery to power a small motor, which cocks back a spring at a very rapid rate. Every time the spring is cocked back it releases automatically (in full auto mode) and pushes out 1 airsoft BB at velocities of up to 400 FPS or more. Most AEG airsoft rifles shoot about 10-14 shots per second, which can easily take out multiple players very quickly.
Another very popular airsoft weapon is the spring airsoft sniper rifles, which generally shoot at a much higher velocity than AEG guns, but are single shot only for the most part. Airsoft sniper rifles are almost always bolt action, and have a much longer barrel than the other airsoft gun types. With an airsoft sniper rifle you have to rely on a lot of strategy, stealth, and extremely good accuracy. This is due to the fact that you usually only get 1 or 2 shots before your opponents figure out your location. Also, airsoft snipers usually end up getting a lot less “kills” than airsoft players who use the fully automatic AEG rifles, since they don’t generally go into direct battle.
The actual airsoft games can vary quite a bit, and are usually determined by the location, the amount of players, and the types of airsoft weapons being used. For example, indoor airsoft matches are usually QCB (close quarters battles), and generally involve short, tactical AEG rifles, such as the M4 carbine for example. Outdoor airsoft games generally offer a bit more versatility, and certainly encourage the use of different types of guns, such as airsoft sniper rifles for example.
Anyone that is looking for an extremely realistic (and fun) way to practice modern warfare tactics and scenarios should definitely look into airsoft. The combat involved in airsoft is much like the real thing, and the airsoft guns look and feel like the real thing as well. Most airsoft machine guns and sniper rifles are actually exact replicas of the real version of the gun, and even have the same weight in many cases too. With that being said and done, it is easy to see why airsoft is becoming such a popular sport.