Contra-alto, literally against the high voice. So, contralto is the female voice that sings (below) against the high female voice. The QUALITY of the voice, and where your voice passagio lies is part of determining if you are an alto (contralto) or soprano or bass, baritone, or tenor. It is not just the range of notes that you can sing. For example, a mezzosoprano has a different quality than a light soprano or coloratura soprano, even though they can all be capable of singing the same range of notes.

Alice