Excalibur is the legendary sword that King Arthur of Britain got from the fairy of the lake. This sword was forged by the elves in Avalon. The blade is made of gold, the handle is inlaid with gemstones, and because of its sharp edge, it cuts iron like mud.

The Caliburn pulled out by Arthur when he chose the king in his youth broke after fighting against King Pellinore in violation of chivalry. King Arthur was very regretful for losing the holy sword. So the great magician Merlin guided him to the holy lake. The fairy in the lake held a sword and lifted it out of the water.

Source: @agoniart