A sword is a long and sharp edged weapon that has been common in many civilizations.
A sword is made of a blade, with one or two edges for striking and cutting, a point for thrusting, and a hilt for gripping.
The length and shape of the sword give away it's main intended use. Swords with a big curvature are intended mainly for cutting. Straight swords are intended mainly for thrusting and stabbing. Many versions are especially made to encounter a specific combat situation. Short swords in tight spaces, Long slightly curved swords for cavalry and light, nimble swords for civilian daily carry.
The Japanese middle length sword is called Katana, has a slight curvature, and is a balance between cutting and stabbing action.
For an extensive Weapon techniques list and videos go to the Traditional weapons portal