Probably one of the best articles regarding how multiplayer games work.

Considering the number of times I've had to argue with people who don't know much about how computers communicate over networks, this article boils down the technical into simple terms that even a layman can understand.

Posted here for future reference should anyone else have to explain why "ping doesn't lag servers" and why "a player with a lower ping against a high ping results in the same time delay for both players".