Breaking into the raid scene can be intimidating for a new player, especially one who's not done anything like 10-man or 25-man raiding. We can hope that 5-man dungeons provide a basic idea of the general dynamics: healers heal, tanks tank, and damagers damage.
Most experienced raiders use language that a new player won't find in the game interface. Words like "tank" have a relatively obvious meaning, but phrases like "void zone" can be a little tougher to interpret when a new player first encounters them. This raider's lexicon has been built through 6 years of WoW raiding, and decades of MMO playing before Azeroth become an MMO.
This guide is intended to help new raiders get an idea what the heck everyone else is talking about. Be warned that most raids also have their own internal lexicon, too; we can't tell you what everyone is saying, but hopefully we'll get you caught up on the most basic stuff.