

The Guild Wars Wiki has an article on Profession.

In addition to their armor class, professions also receive varying amounts of bonus health.

Professions are divided into three categories based on their armor type: There are currently two elite specializations available for each profession: one specialization comes with the Guild Wars 2: Heart of Thorns expansion pack, and the other comes with the Guild Wars 2: Path of Fire expansion pack. Upon reaching level 80, the character gains the ability to train an elite specialization which often changes how the base profession plays. Once a profession is selected for a character, it cannot be changed. Professions are not restricted by race or gender and each is able to contribute damage, control and support during combat. There are nine professions, each with a unique style and theme to their combat approach which is emphasized by the use of an important profession-specific mechanic and access to different skill types and effects. Profession determines skills, traits and equipment available to player characters for engaging in combat and is roughly equivalent to a character class in other games.
