In a lot of video games, as well as most other media-forms, there are usually two types of characters: Those who handle the main-objectives (i.e. the main-protagonist), and those who support whoever is handling said main-objectives (i.e. the main-protagonist's various companions). Sometimes, it's in the form of the soldiers who fight on the battlefield, and the operators who guide their troops from the mission-control room. Other times, it's The Mentor providing teachings to The Hero, who would make good use of said teachings to complete the rest of the mission.