I was reading an answer here a few days ago that was talking about "Holocrons", saying that Kylo Ren might have learned the ways of the dark side from a Holocron.
Are these Holocrons actual Star Wars material? Unless I'm forgetting something major, I don't recall them in any of the films, original or prequel.
How official are these Holocrons? Did Lucas invent them or discuss them at some point? If someone else made them up, did he go on record as saying they are a Star Wars "fact"?