Achievements are in-game awards given to you for accomplishing various milestones in the game. Every achievement in ESO awards you with a specified number of achievement points that accumulate on the Achievement screen. These points serve no purpose other than to give an indication of how much you have accomplished within the game.
A number of achievements will grant you a special title for their accomplishments, while other achievements will unlock specific dye colors for your account for use in the armor dye system.