A fret is a part of some |stringed instruments that allows the player to easily play the desired note without having to finger the neck in exactly the right place. On Western instruments, one fret is installed to correspond to each of the semitones that make up an octave.
They are usually made of metal, and inset in small grooves cut across the fingerboard.
A fret allows a pitch to be matched more precisely and more easily than a non-fretted instrument allows. A lack of frets allows for all of the intervals between two standard pitches to be played. While fretless guitars exist, fretless bass guitars are much more common.
"Fret" can also mean to worry.