The PADD, or Personal Access Display Device, is a hand-held tablet computer used throughout Starfleet for reports, records and reading.
PADDs are among the most common objects on any Federation starship or station. Crews use them to read and sign reports, review technical data, study, and carry information from one department to another, and officers' desks are often piled with them.
Earlier forms of the device appeared in the 23rd century, but it became especially familiar in the 24th, when characters could be found reading novels, writing letters or reviewing duty rosters on a PADD.