The Minotaur was a monster with a bulls head on a mans body. Born in Crete, it was the son of the Queen, Paisiphae. It's father was a snow white bull, sent to the King, Minos, by Poseidon (God of the sea) for sacrafice. Minos thought the bull was too beautiful for sacrafice, did not sacrafice the bull to Poseidon, instead sacraficing a different bull in it's place. This enraged Poseidon, who the cursed Paisiphae to fall in love with the bull. She convinced Daedalus, a brilliant inventor, to fasion her a fake cow in which she could hide. He did, and she hid inside the cow until the bull mated with her. She gave birth to the Minotaur, but as it was a disgusting and shameful creature, so King Minos ordered Daedalus to create a labyrinth in which he would hide the child. This labyrinth was so elaborate that it was impossible to navigate, meaning the Minotaur could never escape. The Minotaur was fed fourteen young Athenian noble men and women, but whether it was fed every year or every nine years is ultimately unclear. The Minotaur was eventually defeated by a young hero, Theseus. He volunteered to go as a sacrafice in order to fight and defeat the monster. The problem was that the labrynth didn't just keep the minotaur from escaping, but everyone who ever entered it. Ariadne, Minos's daughter, fell in love with Theseus, and in an effort to allow him to return, begged Daedalus to tell her the secret to the labyrinth. Eventually he caved in, and told her to give Theseus a ball of string to unravel as he traveled, so he might follow the string back out. Theseus did as Ariadne said, and eventually found the Minotaur and killed it. He followed the string back out and returned safely, freeing Athens and Crete.
See also Daedalus and Icarus: The Labyrinth