Tablature is a method of indicating the position of notes on the fretboard. There are four sets of "tab" lines which represent the strings of the mandolin. Study the following diagram.
The left hand fingers are numbered as such:
When a number is placed on one of the lines, it indicates the fret location of a note e.g.:
This indicates the open (unfretted) 2nd string (an A note).
This indicates the 3rd fret of the 3rd string (an F note).
This indicates the 1st fret of the 1st string (an F note).