This technique involves sliding between two notes on the same string, whilst still fretting the string firmly against the fretboard. If played correctly the sound of the second note is produced artificially (i.e. the second note is not played with the right hand).
The letter "S" and a straight line indicates a slide. If the line comes from below the number, slide from a lower fret. If the line comes from above the number, slide form a higher fret. The number in the brackets is the suggested fret from which to slide. In this situation the first of the two notes is given no time value. In the following example a third type of slide is given: the straight line between two tab numbers indicates the first note should be held for a time value before sliding. Listen to the recording to hear the effect of this technique. The photos illustrate sliding from a lower fret to a higher fret.