Tank

Noun: Tank
Tanks are well armored front row party members whose role is to draw the enemy's attention (aggro) and attacks towards themselves as well as absorbing damage. They block their enemy's way and as such serve as meat shields for the spellcasters and ranged attackers in the back lines behind them. They usually engange foes in melee or PBAoE attacks.

Warriors are the most common form of tank; they have the strongest armor of any profession, and have many skills (especially in the Tactics line) to help them take damage and hold the enemies' attention. Other professions need to be more creative to take the kinds of damage that the tank eats, and so are less common on the whole.

Warrior Tanks
The most common type of tank is a warrior fortified with all possible defensive tactics to soak up as much damage as possible. They will charge the enemy but will focus mostly on engaging the frontline and keeping them busy fighting him/her. Tanks use shields, stances and - if applicable - Protection Prayers to minimize damage inflicted upon them. They can take quite a long while to kill. Tanks can be used as booby traps using AoE spells that are centered on the caster such as Symbol of Wrath, or Balthazar's Aura.

Other Tanks
Some professions, given the right set of skills and proper preparation, can tank for their parties in certain areas. In particular, Rangers, Monks and Elementalists posses in their skill set a number of skills that can be used to make them very resilient to damage. These builds are usually attuned to the monsters in certain explorable areas that do not posses the means to overcome them. A Ranger relying on stances to dodge attacks will not be able to dodge spells while a monk or elementalist relying on enchantments to resist attacks will have problems facing mesmers and certain necromancers who can remove enchantments.

Some popular non-warrior tanking builds include:
 * Invincible Monk
 * Invincimentalist

Verb: to tank
Standing still and taking a beating from enemies instead of running away or kiting. Tanking is often used in PvE to make the healer's life easier (only one person to concentrate on). Tanking is especially effective in combination with Protection spells and stances.

It's important to be conscious of certain expectations while tanking:
 * Tank-on-Tank: This means that when assaulting an enemy group, the tanks should attract the aggro of the enemy melee fighters and keep it focused on themselves. Warriors who rush past the enemy warriors and head for the enemy spellcasters make bad tanks because they allow the enemy warriors to get to their spellcasters.
 * No running back: While tanking, warriors should not, when the going gets rough, run back with their tails between their legs. Instead, warriors should trust their monks and if concerned, they should run sideways and/or dodge. Pulling enemies into the heart of your spellcasters is a sure fire way to kill a few of them as well as get your monks in a panic which means they will not focus on healing you.
 * Keep tanks alive at all costs: A tank that has suffered multiple deaths and is running aroud with, say, 35% DP is of little use to the party in terms of tanking. The reduction to health greatly limits their ability to take damage. As a monk, if you have to choose between healing the tank and healing an elementalist, keep the tank alive. The elementalist can operate with 35% DP from the back if the tank is doing his job, the inverse is not true. A warrior who does not tank and instead rushes off to kill enemy spellcasters forfeits that privilege.
 * Prevention is better than treatment: With the exception of facing powerful mesmers who Shatter Enchantments, a group is best served by using Protection Prayers on their tanks (along with healing) than by just trying to spam healing on them. Protection allows the monks to control the amount of damage inflicted on tanks and thus protects from the unexpected hit that suddenly kills a tank.