What does it mean if you say something is a diamond in the rough?

The phrase "diamond in the rough" refers to something or someone with potential or exceptional qualities that are not immediately apparent due to a lack of polish or refinement. It suggests that, like a raw diamond, the true value is hidden beneath the surface and requires nurturing or development to shine. This expression is often used to describe individuals, ideas, or situations that may initially seem unremarkable but possess great promise.