A character in Star Trek Online is the player's virtual representation of him or herself in the game universe. Characters can belong to one of three playable factions, choose one of several 'faction-aligned' species (or create their own), hold one of three available Professions, have a number of species specific, and player chosen traits, and acquire various abilities.
Several species-specific traits are automatically assigned when the character is created, with an additional trait slot being unlocked every 10 levels (up to level 50). As these slots become available, players can select traits which benefit themselves or their team. Traits are generally chosen based on gameplay sytle, strategic role, profession, or the character's background.
Traits can compliment different roles and professions. For example Defenders (or 'Tanks') will benefit from traits which allow them to take more damage, Damage Dealers are more effective when given traits which allow them to deal more damage, and Healers work best when they have abilities that heal or aid ('buff') themselves or allies and hinder ('debuff') enemies.
Abilities specific to the character's chosen profession are awarded as the character levels up. Additional abilities can be earned from Accolades, the Reputation System, or when equipping certain Items.
Cryptic has created an innovative player customization system. Players are able to create their own races, have many customization options, allowing them control over facial features, size and proportion, and general appearance. This allows players to create races that are unique. Players of all factions are able to use the Alien species to create a custom species in the game.