Have them read this website, especially this FAQ section.
Other than that it's just a bunch of guys playing army.
* (Update 10/14/2007) Have been asked this again and again, so here is another answer.
What we do is not exactly airsoft, call it simulated military operations with airsoft guns.
We hold these scenarios at night, usually on Saturday nights, on a patch of heavly wooded land in Victoria county.
We go out there just after sundown, it's supposed to be in Central America, and it's terrorists vs. American special ops.
We have ambushes, hostage situations, etc. We may encounter trip wires, land mines, all sorts of fun things. We never know if the terrorists will be there or not.
This is a continous scenario. The team is always looking for the terrorists and always have different operations. It's very realistic.