Tab, or tablature, is a musical notation method for stringed instruments that relies on conveying the position of the note on the fretboard and it’s corresponding string.
It achieves this by laying out a diagram of the fretboard, similar to the one below. The line indicate which string the note is on, with the numbers dictating which fret is played next
G –1—-2—-3–
D –1—-2—-3–
G –1—-2—-3–