A small object that is unusual, novel, or interesting, typically one that’s part of a collection of other such objects.

A curio may also be an object that holds some sense of mystery, like a toy from the 1800s, or an old compass that was sold in a seaside shop. There are shops that specialize in curios, or at least what they call curios, which might otherwise be called souvenirs or knickknacks. But if you find them to be curious or novel, they’re curios.