Tom Marvolo Riddle, a half blood, was educated at Hogwarts School of Witchcraft and Wizardry.  He was placed in Slytherin House, and later became Head boy.  

After leaving school he traveled far and wide, disappearing from the public eye.  When he reappeared, he had named himself 'Lord Voldemort', the name which is now feared beyond any other for the mass destruction of Muggles and Muggleborns.  

Tom Riddle always had a hatred of muggle born people from his earliest days at a muggle orphanage.  Placed there by his mother, who later died, Tom never got to know his Father, who abandoned his Mother after learning she was a witch.  Bitter and angry, Riddle's hatred of muggles and muggleborns stemmed from there.  

After learning he was the 'Heir of Slytherin', Riddle placed himself with the task of eliminating muggles and muggleborns from the world.  He gathered loyal Slytherin's as well as traitors from other houses and formed his group, the Death Eaters.  

A Death Eater is distinguishable by a tattoo like imprint on their forearm, of a skull formed of stars with a snake protruding from it's mouth.  This 'Dark Mark' is shot up in the air whenever the Death Eaters have made a killing. This was also used as a method of communication between Voldemort and the other Death Eaters. Whenever Lord Voldemort used to touch the Dark Mark on the arm of one of the Death Eaters, the others were alerted. They would then have to disapparate and apparate to where Voldemort was. He used this method to call all Death Eaters to himself in the graveyard near Riddle House, in book 4.

The fall of Lord Voldemort happened when he tried to kill the son of James and Lily Potter, Harry Potter.  The killing curse - Avada Kedavra bounced off Harry and hit Voldemort himself, ripping him of his powers.  Voldemort hid from public view for more than 11 years, a broken and defeated wizard before he appeared again, ready to try to take over the world, for the second time.  Thwarted once again by Harry Potter, Voldemort tried another time before, on his third attempt, was restored to his former power.  

Death Eaters under his control, former power restored, Voldemort is now ready to take over the wizarding world.  Snake slit red eyes, flaring nostrils and a papery white face, are what remain of what was once a handsome black haired boy.  Such is what the Dark Arts can do to people.