Caption: Tasha prepares to fight
The generic name, especially in use aboard Federation starships, for the "smart" virtual reality system as evolved by the 2360s — a technology that combines transporter, replicator, and holographic systems.
The programs, projected via emitters within a specially outfitted but otherwise empty room, can create both "solid" props and characters as well as holographic background to evoke any vista, any scenario, and any personality — all based on whatever real or fictional parameters are programmed.
While personal holoprograms relieve the stress and isolation of shipboard life for crew personnel, Holodecks are also used for tasks ranging from scientific simualtion to tactical or even covert training. Off starships, many commercial users have equipped facilities with so-called Holosuites.