A harmonic is a chime like sound created by lightly touching a vibrating string with a left hand finger at certain points along the fretboard. The sound of harmonics should be bright and clear with lots of sustain. Once a harmonic has been played and keeps ringing it is no longer necessary to touch the string with your fingers. For best results pluck the string near the bridge and boost the treble control. Harmonics are usually higher in pitch than fretted notes and are great to add as extra notes. The most common harmonics are found on the 12th, 7th and 5th frets. To play these basic harmonics position any finger of your left hand directly above the relevant fret just touching the string without pressing down.
Harmonics are indicated: harm.
The following chart shows you where to obtain harmonics on the fretboard.