Are you one of a kind? Then you must have some kind of uniqueness, some quality that makes you stand out from all the rest.
When you break down the word uniqueness, it’s easy to see what it means. First you notice the word unique, which means “one of a kind.” Then you notice -ness, a common suffix that’s used to form nouns that refer to a state of being. Put it together and you get uniqueness, a noun used to describe that certain something that makes a person or thing uncommon or singular, like "the uniqueness of a famous opera singer’s voice."