Gaff Rig
Gaff topsails, like gaff rigs in general, may still be seen today but were once more common. The gaff rig has been largely superseded by the bermuda rig, which has no topsails. On a gaff rigged sailing boat, topsails may take a few different forms:
A gaff topsail is generally a triangular sail set between the gaff and the top of the mast or topmast. A gaff-rigged vessel might have a gaff topsail above any or all of its gaff sails.
A yard topsail is like a gaff topsail, but is extended higher by a small vertical yard.
A jack-yard topsail (or Club topsail) instead has its lower edge (or foot) extended out beyond the end of the gaff with a short yard, called a "jack-yard". A jack-yard topsail may also have the aforementioned vertical yard, although this makes for a very large topsail.
A square topsail is a square-rigged sail, generally carried above the foresail when on boats with multiple masts. Gaff-rigged vessels carrying square tops are referred to as "square-topsail sloops", "square-topsail schooners", etc. Occasionally this is shortened to simply "topsail sloop" or "topsail schooner", although this term can apply to vessels carrying topsails of any kind.
A raffee is a square-rigged topsail which is triangular in shape.
Read more about this topic: Topsail