One of the most daunting tasks players will be faced with in Final Fantasy XIV is deciding what job role to fill. Jobs are essentially specialized classes that have abilities designed to perform specific functions in a group, which means a player's job choice affects not only them but also the people they play with. This makes a player's job role one of the most important decisions they will ever make in the game.
Source:https://www.cbr.com/ffxiv-newbie-job-role-guide/