This instrument will allow you to play bass notes on the wound strings to accompany yourself with a lower range of notes.
The standard arrangement gives a repeat of the lowest 8 notes of the normal bass bridge an octave lower and that can be tuned up or down by a semitone. The low bass strings can be played either to the left or right of the instrument.
The normal right hand bridge is playable on both sides too with note on the right 2 octaves higher than the normal range of bass notes.
This instrument looks and sounds great! I have made a selection of these all looking a bit different. There are options on the standard instrument but people often commission special versions.