If you're interested in PvP in any way whatsoever, you've probably heard of a little statistic called Resilience. Introduced a little before The Burning Crusade was released, Resilience reduces the chance a player will be struck by critical strikes from spells or attacks. It also reduces the damage taken from critical strikes and Damage-over-Time (DoT) spells. It is a landmark change in PvP mechanics, qualifying as the most important improvement to World of Warcraft PvP since the game was launched. With the introduction of this new item property, PvP became less a matter of damage output -- although that's still important -- and more a matter of survivability or, well, resilience.
Battles are now intended to last a little longer, Resilience greatly reducing the chances of frustrating (for the recipient, anyway) instagibs. Prior to Patch 2.0, the premiere PvP stats used to be Stamina and Spell & Attack Critical Strikes, which were abundant in PvP-obtained items. However, both item properties were often also useful in PvE, which made many PvP items desirable even outside of PvP. Conversely, the sheer strength of PvE raid items were dominant on the PvP front, in many cases overpowering Stamina. This changed with the introduction of Resilience, which drew a defining line between PvP and PvE gear. With the new mechanic, in order to PvP more effectively, one had to wade into the thick of battle and earn Honor or Arena points. All players will start off with no Resilience, and it takes a conscious effort to accumulate the gear for it. Before undertaking such an endeavor, let's take a look at other forms of damage mitigation that are more accessible in the beginning stages of acquiring Resilience gear.