Spock was the science officer and first officer of the Constitution-class starship Enterprise, carrying the rank of Commander at the time. As the child of a Vulcan and a Human, he set the precedent for having a half-human hybrid on practically every Star Trek series.
Following the ship's five-year exploration mission, Spock returned to his homeworld to try to achieve the Vulcan ideal of completely logical behavior, but the approach of the space probe V'Ger distracted him from this goal. He returned to Starfleet, eventually achieving the rank of Captain before turning to political service as an ambassador.
Spock has been played by Leonard Nimoy in every incarnation except for the eleventh Star Trek movie, in which he is played by Zachary Quinto. Nimoy, however, appears in the movie as "Spock Prime".