Tablature is essential in learning to play pieces in open tuning. Even good music readers will have difficulty in reading music in open tuning because with each open tuning, notes are found in different places on the fretboard.
Tablature is a method of indicating the position of notes on the fretboard. There are six "tab" lines each representing one of the six strings on the guitar.
When a number is placed on one of the lines, it indicates the fret location of the note e.g.:
This indicates the seventh fret of the 5th string (an E note in standard tuning).
This indicates the 3rd string open (a G note in standard tuning).
Tablature symbols are used to indicate a left hand technique.