The adjective esoteric means something different that is known or liked by only a limited number of people.

Synonyms are mysterious, arcane, mystical, or hidden.

The word origins from Greek (1650s) esoterikos meaning “belonging to an inner circle”, from esotero meaning “more within”, comparative adverb of eso meaning “within”. It is classically applied to certain popular and non-technical writings of Aristotle, later to doctrines of Pythagoras. In English, it means the first of Pythagorean doctrines.

Her esoteric interests set him apart from her friends.

He delivered an esoteric speech.

It was considered as an esoteric plan.