A foil is a type of sword used in fencing.
It is a very thin sword, with a blunted (or foiled) tip, designed only for stabbing with this blunt tip, and flexible enough to bend when striking an opponent. There are three main types of foil, the most common being the French style, with a grip (handle or hilt) designed to facilitate greater finesse. Other types include the Italian style, which is designed more for control and power, and the orthopedic, or pistol-grip, which takes the need for a firm hold on the weapon even further. Critics of the pistol-grip, however, claim this leads to a "deathgrip" on the foil and inhibits true mastery.
The modern foil is descended from the training weapon for the small-sword, a lighter version of the rapier that was the common sidearm of the 18th century gentleman. (Rapier and even longsword foils are also known to have been used but they were very different in terms of weight and use.)
In modern sport fencing, the foil is used as a stabbing weapon only; to score a point, one must stab an opponent with the tip of the foil with a force of at least 4.90 Newtons (500 grams). The valid target area at foil is limited, due to it having evolved from the time when fencing was practiced with limited safety equipment. Hits to the face were dangerous, so the head was removed as a valid target. The target was then further reduced to only the trunk of the body, where the vitals are located. A touch which lands on nonvalid target stops the fight, but no point is scored.