A holocron, short for holographic chronicle, was an organic crystal-lattice device, in which the Jedi, as well as the Sith, of old stored phenomenal quantities of data, as well as the holocron's gatekeeper. The Sith also had their own form of holocron technology, and they seem to predate the Jedi in using the technology by at least three thousand years.
"Meant to be a teaching device. Jedi record their experiences into them. They're interactive so you can talk with them."BTW, Quinlan Vos is one of my favorite Jedi Masters. You can read more info on Holocrons and Master Vos here:
―Quinlan Vos
Holocrons:
http://starwars.wikia.com/wiki/Holocron
Quinlan Vos:
http://starwars.wikia.com/wiki/Quinlan_Vos