Tabulature is music notation for lute. Unlike notes, it does not represent which sounds play, rather shows which fret to hit. Most of lute pieces have been written in that way.
Elizabethan tabulature is most common tabulature.
G____________________ D____________________ A____________________ F____________________ C____________________ G____________________
It represents six courses, from lowest string to highest string. Letters are used to show which fret to hit. A is empty string, B is first fret, C is second fret, D is third fret, E is fourth fret, F is seventh fret, G is eighth fret, H is nineth fret, I is tenth fret, except there is no J, because it was thought that it could be mistaken with I.