Expertise

 (prior to Season 6: Bridge Officer Skill Points) is used as a cost for applying a Training Manual on a bridge officers, teaching them new abilities. Cost of Expertise is increased with the number of abilities the BOff already possesses. Expertise is also needed as a contribution to certain projects of the Reputation System, as well as the Fleet Advancement System.

Just like Experience Points, expertise is earned indefinitely by playing almost any content of Star Trek Online, e.g., defeating NPC or player enemies, completing missions/assignments, and so on.