"Gatekeeper" was the term used for the artificial personality that granted a user access to the information within a holocron. The gatekeeper was usually based upon the creator of the particular holocron, or a later owner that contributed their own knowledge to it. The gatekeepers of Sith holocrons were sometimes the consciousnesses of the certain Sith who actually created them.
Famous Jedi gatekeepers included Bodo Baas and, much later, Luke Skywalker. They taught the finders of the holocron everything that the creator had discovered in their life. The gatekeeper itself held access to whatever information was hidden inside, and chose whether or not the student using it was worthy of the holocron's knowledge. While the gatekeeper was unlikely to find someone unworthy, it could refuse to teach them more until it decided they had mastered what it had already taught them. The gatekeepers of Sith Holocrons were known not to limit access to the holocron's information, often teaching the user things that were far too dangerous and advanced for them, that would more often than not lead to their destruction.