An Exorcist (祓魔師Ekusoshisuto) is an individual with the abilities and training to combat Demons. Throughout the history of Assiah, there have been many different groups of Exorcists that protect humanity against these malevolent entities.
Before becoming an Exwire, the individual begins as a Page, learning the most basic elements of exorcism and Demonology. To become an Exwire, a Page must pass the Exwire Authorization Exam. The exam consists of both written tests and a field test, which determines the class' overall combat abilities and teamwork skills.
Exwires (候補生Ekusuwaia) are student-Exorcists ranked directly above a Page. Exwires still attend classes and study to become Meisters, but are able to perform non-combat missions, such as maintenance and errand running.
A Meister is someone who has the knowledge to become an Exorcist. Essentially the most basic qualification for any aspiring Exorcist, the term Meister refers to the particular combat skill(s) an Exorcist possesses. There are five different classes of Meister in which individual can become qualified.
Lower Rank Exorcist
Lower Class (下級Kakyū) or Junior exorcists. These are the lowest rank of qualified Exorcists. They will sometimes supervise Exwires on simple missions.
Paladin (聖騎士Paradin) is the highest rank of Exorcist. There can only be one Paladin at a time and, typically, once an individual becomes the Paladin they keep the title until they are deceased. The appointment is exceedingly difficulty, with the minimum conditions being that they completely learn all five meisters. In the anime, it's suggested that Paladins are allowed to choose a new uniform with the color of their choice, given Arthur wears a modified white uniform and Yukio wore a green version of his normal uniform.