The art of armed combat using a sword.
Today fencing falls into 2 broad categories:
The future of fencing using somewhat stylized weapons (Foil, Epee and Sabre) that are extremely cut down, 'tuned' versions of the original deadly weapons (Small sword and Sabre). Weapons are probably made of space age composite materials. Sports fencers are athletes, train accordingly and compete in the Olympics (boring cnuts). Scoring in a bout can be done by electronic scoring (a completed circuit thought wired weapons) although some cnuts have cheated by the addition of a battery up their sleeve, a button to connect the circuit and a little extra wiring.
Due to the stylized nature of sports fencing ... dont expect anything like an Errol Flynn movie. Many rules have had to be brought in to stop simultaneous attacks (right of way), non valid targets areas and even (in Sabre) to stop fencers leaping 5' in the air/at each other as soon as the bout starts in the hope of a quick win.
The past of fencing where the techniques that make swords real weapons are rediscovered from medieval and renaissance manuals (called treatises). Using steel swords (fortunately blunt), these guys are usually found training in the pub. Extremely argumentative these F'ers all have their own opinion about how it was really done although only the terminally sad (usually Spams) argue about footwear being crucial to understanding technique.
Freeplay (a duel) between these guys usually ends up looking like something from the storming of Constantinople and as long as both parties walk away with most of their limbs still attached, anything goes. Mild walts but hey ... like they care! In this overly controlled nanny state, they've got swords and a legal right to use them.