Data was a collection of information that was amassed through observation. Being anything, data had little or no meaning and was not useful until it was processed, organized, and presented in context.
In 2266, during Harcourt Fenton Mudd's hearing, the USS Enterprise computer displayed data on his offenses on the tri-screen viewer. The computer found no data on Mudd's women. (TOS: "Mudd's Women")
During The Voyager Encounter holoprogram, Captain Kathryn Janeway requested all tactical data regarding the war between the Vaskans and Kyrians; data which included Kyrian defenses and the position of Vaskan forces. (VOY: "Living Witness")