A clef is a musical symbol placed at the beginning of a staff to indicate the pitch of the notes. The most common clefs are the treble clef, which represents higher pitches, and the bass clef, which represents lower pitches. Each clef assigns specific notes to the lines and spaces of the staff, helping musicians read and interpret music accurately. There are also other types of clefs, such as the alto clef and tenor clef, used primarily for certain instruments like the viola and trombone. Clefs are essential for musicians to understand the range and sound of the instruments they play.