sniffing

In many posts on hnm camping, I see packet sniffing brought up. It's always the same thing. "We know they were packet sniffing because a minute or so before he popped, the entire team converged on a single location..." My question is: what's everyone else doing while 18 people converge on a...

Found these posted on Alla today..... Thought I'd post em here to see what you guys thought of em... Crazy videos that show someone counting down up to a minute before the HNM spawns.... when the person reached 0, sure enough, HNM spawned..... http://www107.sakura.ne.jp/~hnm/Jonesz.avi...

ok ok I am not a computer guy i know very little and i really want to know what exactly packet sniffing is