A skill was a learned ability which could be performed well.
In 2267 while Spock was on trial for mutiny, José I. Mendez was amazed at Spock's technical prowess in somehow showing events from thirteen years prior on a viewscreen. (TOS: "The Menagerie, Part I")
In 2366, nanites that had infested the USS Enterprise-D's computer core were working with a new collective intelligence, operating together and teaching each other new skills. Later, according to Lieutenant Commander Data, the nanites entering his neural network would require no more than their most basic skills. (TNG: "Evolution")
The Doctor was adept in the art of holographic programming. (VOY: "Living Witness")