Mezzo-soprano is the female voice type between soprano and alto. Mezzo just means "middle" or "medium" in Italian. Typically, the mezzo range extends from the A below middle C to the A two octaves above (A3–A5 in scientific pitch notation, where middle C = C4). The timbre tends to be rich and creamy.
There are different types of mezzo-soprano depending on the quality of sound and weight of voice: lyric (warm tone, long flowing phrase), coloratura (high and florid), and dramatic (heavy and dark).
In sheet music, mezzo is a direction for the tempo to be played at medium speed.