This page contains information regarding Star Trek: Discovery, and thus may contain spoilers.
A library computer, occasionally referred to as ship's library or computer library (of records), was a component in Starfleet ships, that could be crosschecked for information on a variety of topics, including planetary systems, medical information, ship manifests, historical events, and cultural customs. (TNG: "Skin of Evil", "Lonely Among Us", "The Emissary", "The Naked Now"; Star Trek V: The Final Frontier) Even obscure writings might be found in the library computer. (TAS: "The Infinite Vulcan")
USS Discovery had multiple library computers. After a a spaceborne lifeform transmitted its knowledge to the ship, all library computers were processing at 20% above maximum. (DIS: "An Obol for Charon")
On Galaxy-class ships, Library computer access was controlled by Subroutine C-47 of the computer core. (TNG: "A Fistful of Datas") Its library systems could be allocated to Stellar Cartography, which would temporarily bring the library computer offline. (TNG: "Lessons") Research logs could be integrated with the library computer. (TNG: "Homeward")