The sail is striking.  A trapazoid rather than a tall and thin triangle, the gaff sail has a feeling of old-world character.  Here, from John Leather's The Gaff Rig Handbook,  are the two basic types of main sails seen on gaff rigs.  The shorter side of the sail, along the mast, is the luff, and working counter-clockwise, we find the head at the top, the leech along the longer side and then the foot at the bottom.  "A" has the sail laced to the boom, while "B" is loose-footed. On both, the sail is supported at the head by the gaff (with lacing) and along mast the luff is either laced directly to the mast or to mast hoops.  The luff is attached to the boom at the cringle.  It is laced to the boom along its length in "A".  For loose footed mainsails as in illustration "B", the clew, the lower left corner of the sail in these illustrations, is attached to the end of the boom.  The loose footed mainsail allows more adjustment of the "belly" of the sail, which helps catch more air.

The halyards, or "ropes" that control raising and lowering the sail, are the peak halyard and the throat halyard.  The peak halyard is attached to the gaff, toward the end away from the mast, and is used to adjust the angle of the gaff upward to trim the sail.  The throat halyard attaches to the gaff near the jaws, and raises that portion of the gaff until the luff is straight.

The main sheet, or rope that allows the sailor to swing the boom from side to side to adjust to the wind, is much like the main sheet on a bermudian or marconi rig.  The detail pages will show some provisions to finely tune the gaff sail.