
The Foil

The weapon that most beginners learn to use is the foil. This weapon evolved as a practice weapon for epee, and so is a smaller, lighter version of the epee. A foil bout involves more rules than an epee bout. Also the target area for foil is limited to the body, with hits to the arms, legs and head being disallowed. These rules are designed to make the fencer aware of good form and movement. Once the basic techniques have been learnt, then the fencer moves on to either epee or sabre.
The Epee

The epee is a larger, stronger version of the foil with a larger guard. The rules of epee are a lot simpler than foil, in that an attack to any part of the opponent's body is considered a hit. In ancient times the epee was used as a dueling weapon. If two lords had a dispute they would fence in epee until the first blood was drawn (Or until death, depending on the insult).
The Sabre

The sabre is the slashing weapon of choice. The only hits that register are those made with the cutting side of the blade or by stabbing with the tip. This weapon was originally designed as a cavalry weapon so you can only strike your opponent above the waist as this is the only target you could aim for from horseback. The head and wrists are both legitimate targets. Sabre attacks are a lot faster than epee or foil and so matches are a lot shorter. Because of the nature of the weapon, attacking is encouraged over defence.