Primary Attribute

Each profession has a powerful primary attribute available only to characters that have chosen that profession as their primary profession. For example, when chosen as a primary profession, the Ranger possesses Expertise, which reduces Energy cost for using certain skills; while the Mesmer can put points into Fast Casting, which increases spell casting speed. The secondary profession you choose will not have access to this primary attribute, so it's important to note each profession's primary attribute when considering which profession will be your first choice. http://www.guildwars.com/gameplay/gettingstarted/attributes/