A short guide to some common terms that appear in other PvE guides.
Add - an additional enemy that appears as you are fighting the main boss.
Aggro – To gain the attention of an enemy (or group of enemies), causing it to enter a combat state and attack players.
AoE – Area of Effect; refers to the area in which an effect occurs – typically a circle.
CC – Crowd Control; referring to skills or the use of those skills in order to break Defiance Bars or control enemies without a Defiance Bar. CC effects are divided into two kinds - "soft" and "hard". Soft CC refers to control effects inflicted via conditions, which reduce the effectiveness of the target but do not completely disable it. Hard CC refers to control effects that completely disable the target. The Fear and Taunt conditions are the only conditions that are considered hard CCs.
Cleave - The ability for skills to hit enemies other than their primary target. Typical usage refers to the incidental killing of enemies close to the boss without having to focus on them specifically.
Defiance Bar – A blue bar that appears underneath the health bar of certain enemies. This bar has a value, and CC effects will reduce this value. Once it is depleted, the enemy will be “broken” which will interrupt its current action and may additionally make it vulnerable.
DPS – Damage Per Second; refers to the action of damaging an enemy, or classes that are taken to fulfil a damage-dealing role in the group (contrasting with supports). DPS builds divide into "power" or "condition" (condi) types, determined by the stats on their equipment.
Evade – Certain skills allow you to temporarily evade attacks, ignoring their effect. The act of dodging makes you evade for 0.75 seconds.
Flanking - Some skills or traits will do only activate or deal more damage while you are flanking a target. Effectively this means being positioned anywhere other than in front of the target.
Hitbox - The area in which a target "exists", used for determining whether skills hit the target or not. The circle underneath a selected target gives some indication of the hitbox size as well as indicating where the center of their hitbox is.
ICD - Internal Cooldown. Many traits or effects will not trigger all the time, but instead have a hidden cooldown that has to pass before the effect will trigger again.
Kite – An action similar to tanking where a player stands at a distance from a boss in order to keep certain attacks away from other players.
Split Phase – A phase of an encounter where the boss ceases to be attackable. Players will generally need to perform some other task before they can re-engage with the boss.
Support – a class whose role is generally to provide boons or healing to the group (contrasting with DPS).
Tank – A specific player who has the attention of an enemy is considered to be “tanking” it. There are various methods by which this attention is decided, but a common one is that the player with the highest toughness stat will be the tank. If at any point the condition for tanking is superseded by anther player (e.g. another player gains more toughness than the current tank), then that player will become the tank instead. Typically, tanks are expected to move bosses to specific locations and keep them still whilst surviving the bosses attacks.
Wipe – The act of killing all players and failing an encounter, usually in response to a failed mechanic.