What It Means: Holing up in a reasonably secure location, waiting for the hapless n00bs to approach, and serving them a nice tasty lead salad.
Why You Hate It: Unless you go all the way around the map, there's only one way to get at the super death ray, and it's right past this path; but that guy on the other team simply insists on gunning down anyone trying to use it. Why the hell hasn't he run out of ammo yet?
Why You Do It Anyway: Because it works, not to put too fine a point on it. Sure, in your heart of hearts you know it's not really fair, but this is war. If you can kill the other guy without him being able to kill you, then the hell with a sporting chance. Your K/D ratio is much more important than his.
Besides, you'll be damned if you're gonna let the other team have the super death ray.
What It Means: Really? Okay, for those of you who go out of your way not to know things, sniping is using a long-range weapon against some poor bastard way over there, and dropping him without him ever being the wiser.
Why You Hate It: Half the fun of playing this game is getting to watch the guy who thought he was a badass crumple at your feet. Face-to-face, when you're the crumpler, you can see the crumplee. When the roles are reversed, at least you know you lost a fair fight to a superior opponent.
Getting sniped changes everything. You don't even know why you're dead there's no one anywhere near you and no grenades went off. It's pretty damn hard to defend yourself against an enemy you can't even see.
Why You Do It Anyway: It's quick, easy, effective, and involves almost no danger for you. Basically you become the hand of God, smiting the lesser beings who dare to challenge your supremacy from a place of complete safety.