A quarter rest is a musical symbol that indicates a silence lasting for one beat in a piece of music. It is represented by a small rectangle that sits on the staff. Musicians use quarter rests to create pauses, allowing for a break in the sound and adding variety to the rhythm. In the context of music notation, quarter rests are essential for maintaining the structure of a composition. They help to define the timing and flow of a piece, working alongside notes like quarter notes and eighth notes to create a balanced musical phrase.