Attribute

Attributes
Every profession has 4 or 5 attributes, one of them being the primary attribute of the profession. The primary attribute of a profession is only available if the respective profession is also the character's primary profession. For example: an Elementalist/Mesmer has Energy Storage and all other Elementalist and Mesmer Attributes except Fast Casting, while a Mesmer/Elementalist has Fast Casting and all other Mesmer and Elementalist Attributes except Energy Storage.

Rank
Ranks are the cornerstone of your character's development. Their values indicate, among others, how powerful a character's Attribute Skills of the respective attribute are.

To increase the rank of an attribute you use Attribute Points (AP). The maximum possible number of AP you can have is 200. For details about how to collect AP read: Attribute Point

The maximum base rank an attribute can be raised to using AP is 12, but the final rank can be modified by various methods:
 * The most common of those methods is using a Rune of the corresponding type, which give a character an attribute bonus of up to +3. Note that positive Rune effects of the same type do not stack, so having a Rune of Minor Fire Magic and a Rune of Superior Fire Magic equipped at the same time still gives +3 instead of the expected +4, because only the highest positive effect counts.
 * The second-most common method is wearing various Headgears, which can give a +1 bonus to one attribute.
 * The third method is using a weapon and/or a Focus Item that has the ability to give a +1 bonus to an Attribute when the player uses a skill. This ability is always chance-dependant and has a variable chance of success (10-20%). Because wands and shields don't have the +1 ability, no profession has a chance of a total +2 Attribute bonus with this method.
 * The fourth and last method to increase an attribute's rank is only available to Necromancers and Elementalists. Necromancers have the spell Awaken the Blood, which gives them +2 Blood Magic and +2 Curses for a certain time span. Elementalists have the Glyph of Elemental Power, which boosts all elemental attributes (Air Magic, Earth Magic, Fire Magic, Water Magic) by +2 for the next spell.

All this means that the maximum rank a character can achieve in a single attribute is 12 + 3 + 1 + 1 + 2 = 19

Many players prefer to specialise in 2 or 3 attributes to make most effective use of AP, since only 200 AP can be gained by the time you reach the level limit of 20. For example, a monk dedicated to healing might decide to have 12 rank in both Healing Prayers and Divine Favor, making as much use as possible out of the healing abilities that a monk posesses. This would cost 194 AP in total, but allow basic healing spells to be considerably more effective; with Healing Prayers and Divine Favor both at 12 Orison of Healing will heal for 98 Health (60 from Healing Prayer and the rest from Divine Favor, which adds 3.2 health for every rank) compared to a mere 20 Health with both attributes set to 0 rank.

However, because of the quickly diminishing returns of higher ranks, it is a viable strategy to diversify into 4 or more attributes if a Build requires doing so.