Meaning of the word "hidden gem" in English

What does "hidden gem" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

hidden gem

US /ˈhɪd.ən dʒɛm/
UK /ˈhɪd.ən dʒɛm/

Phrase

something that is extremely good but that few people know about

Example:
That small restaurant downtown is a real hidden gem.
The museum is a hidden gem for art lovers.