A Sith Holocron is a device that contains dark secrets of the sith.
A Holocron is basically a hologram that stores important information or things that need to be saved. Some of these items, can include star maps, Sith Holocrons, Jedi Holocrons and a variety of other holographic things, Holographic generators can be stored in a special base or in certain droids. Basic Holocrons are set up in basic Fashion. There is a special source of power located in a base unit. Once this source is dead the holocron becomes useless, unless it is a re-chargeable source. There is usually a small holoport that displays the image, which can be fully animated, such as rotating plans, or a fully talking figure of a human, repeating a messege.