Grew up playing this. It is an epic sport. A LOT of fun, totally cheap, and does wonders for your sprinting and the ability to change direction.
Basically, you cross the line shouting "Kabbadi" and in ONE breath, you have to touch a member of the opposite team and get back over your own line. Their job is to keep you on their side of the line until you run out of that breath. The continuous shouting proves that you're doing it all in one breath.
It is simply AWESOME.