Born Tom Marvolo Riddle, he was raised in an orphanage after his mother died during his birth, and the father, a muggle (non magical person) wanted nothing to do with him, his family, or his mother. Described as being a very handsome young man resembling his father, and remained that way up until his later years (thirties to forties)
Even at a very young age, he was shown to have control and a little bit of skill with his magic. Is also seen as a bit psycotic even during his pre pubescent years, and thinks that Dumbledore is a doctor coming to take him away.
During school, he was sorted into Slytherin. He was very, very gifted, and even won the 'special services to the school' for getting rid of the man who opened the chamber of secrets (this is later found out to be false, and he in fact opened the chamber.) He was head boy during his seventh year. Directly after graduation, he applies for a job teaching at Hogwarts, but Headmaster Armando Dippet turns him down, saying that at eighteen he is too young. He then goes to work for Borgin and Burkes instead.
Around ten years later, he reapplies as Defense Against the Dark Arts teacher, but headmaster Albus Dumbledore refuses. The job has been cursed ever since, with each teacher not staying more then a year.
He then began to gather followers who believed in his ideology of pure bloodwizards being superior, and that half bloods, (which in fact he was one) muggle born's, and muggles, were not worthy of living. His followers called themselves Death eaters, and they are marked with a skull and snake burned into there forearm. It is known in at least one case with devoted and only female follower, Bellatrix Lestrangenee Black, that Voldemort himself taught and trained her in the dark arts. It is unknown whether or not he did this with any other follower. Some fans of the series say that he and Bellatrix were a romantic item, and author JK Rowling said that in fact, Bellatrix "truly loved Voldemort". It is unknown weather or not he returned those feelings.
At the height of his power, he heard of a prophecy, saying that a boy born in the end of July would be his downfall. It is then that he went to the Potters and attempted to kill the main protagonist of the story, Harry Potter. However, the curse rebounded, and left Voldemort in a state a little better then death.
Eleven years later, he inhabited a man named Professor Quirrell in attempt to steal the Philosophers stone (Sorcerers stone in the American and film version) in order to regain his former strength. He was thwarted, however by Harry, and when Professor Quirrell was killed, he left the body without the stone
One year after that, his diary from school was given to Ginny Weasley, a first year and sister to Harry's best friend Ron Weasley, by Lucius Malfoy. It was unknown to Lucius that the diary was a horcrux, a magical item in which a dark wizard puts a piece of his soul. It inhabited Ginny and forced her to open the Chamber of Secrets and attempt to murder several Muggle born wizards. Later in the film, Harry, Ron, and DADA professor at the time, Professor Lockhart, went down in to the chamber and whale Ron looked after Lockhart (he had cast a powerful memory charm on himself), Harry fought not only the Basilisk, but a teenage Voldemort. After he killed the Basilisk, he used one of the fangs to stab the diary, 'killing' it in a sense.
Two years later, Voldemorts loyal servant Wormtail, (who betrayed the Potters) brings Voldemort back to life, using Harry's blood, Voldemorts fathers bone, and his own hand. The potion works, and Voldemort returned. He then called his followers, a majority of which return to him. Voldemort fights Harry, and a strange thins happens in the midst of there battle. When they cast a spell at the same time, there wands connect, and Voldemorts wand 'regurgitated' the spells he last cast. Harry sees his mother, father, and Cedric, a boy killed by Voldemort just minutes before, and they tell him what to do. When they tell him to break the connection, Harry does, grabs Cedric's body, and the Triwizard cup (a port key that brought Harry to the dueling spot) and he goes back to Hogwarts, leaving Voldemort angry, and at full power.
One year later, he breaks his most faithful out of Azkiban, a wizarding prison, and then orders them to go to the Hall of mysteries and steal the Prophecy containing him and Harry. He has also begun invading Harry's mind, using fake images of his god father, Sirius Black being tortured by him at the hall. Harry along with several of his friends go to the hall of Mysteries, believing that the images are true. A battle insures, in which the prophecy smashes, and Bellatrix kills Sirius (her cousin) and Harry for the first time uses a unforgivable curse. It is ineffective however, as he didn't really want to torture her, and was just angry. She refuses to believe it is broken until Voldemort himself shows up and tells her that Harry is not lying. She begs for mercy, but he ignores it. Soon after, Dumbledore shows up and begins dueling with Voldemort. They are both equally matched, and for a mere second, it appears that Dumbledore has won. However, Voldemort inhabits the body of Harry and quotes the headmaster, saying that "if death was nothing, then why not kill the boy?" He leaves soon after however, grabs Bellatrix, and gets spotted by the minister of magic.
One year later, he is at the height of his power, using the Malfoy manor as headquarters, and is scared for the first time of Harry finding out about his horcruxes. He has taken over the ministry, and attempted to kill Harry while he was traveling to safety to a member of the Order of the Phoenix, a group dedicated to defeating Voldemort. However, Harry's wand acted on its own accord and shot a spell directly at Voldemort. He is afraid for his horcruxes, but is positive that he would have felt it if they got destroyed. In any case he keeps his snake Nigini, a snake where he kept another part of his soul, close at hand. He discovers that Harry stole his locket, another horcrux, and in turns destroys it. He also discovers that Dumbledore destroyed his ring (another horcrux.) Later in the book, Harry, Ron, and Hermione (disguised as Bellatrix) break into Bellatrix's vault and steal Helga Hufflepuff's cup, another horcrux. When he finds out, he is very, very angry and goes on a killing spree in Gringotts, leaving only Bellatrix and Lucius alive (they scampered before he had a chance to kill them, and in my opinion, he wouldn't of killed them, both being very high up in his inner circle.) He then goes to Hogwarts, where the golden trio goes to attempt to destroy the cup and find the last horcrux. They succeed and all the Horcrux's left now are Harry himself, and Nigini. A battle insists, where his followers all fight the supporters of Hogwarts. He calls them off, saying that if Harry gives himself up, then he will give them mercy. They have one hour. He then goes and hides in the forbidden forest with the surviving death eaters. Harry comes to him eventually, after seeing the memory of Snape after Voldemort kills him in order to have control of the Elder wand, a wand that can not be beaten if someone takes it from there current master. Having Snape killed Dumbledore (the last holder of the wand) Voldemort assumes that Snape is the true master, unaware that the death of Dumbledore was planned by Dumbledore himself and Snape two years before hand. He is unaware that Draco Malfoy, the wizard who disarmed Dumbledore, is in fact the real master of the wand. But then Harry disarms Draco while captured in there mannor, making Harry the master of the wand. After Harry sees the memory in which Dumbledore tells Snape that Harry must be killed by Voldemort in order to defeat him, he goes to him. Voldemort then kills him, knocking himself out in the process. He is unaware that when he tried to kill him years ago, he made Harry a horcrux. Harry does not die, but Voldemort is told by Narcissa Malfoy that he is however, wanting to enter the castle and save her son. They go into the army, and Voldemort falsely tells them that Harry is dead. Fighting continues however, and eventually the only people left fighting for him is Voldemort himself and Bellatrix. Bellatrix is murdered by Molly Weasley, and Voldemort is very angry and attempts to kill Molly. Harry then reveals that he is alive, and he protects Molly. They circle each other for a few minute's, Harry telling Voldemort that he is the true master of his wand, and reveling that Snape was Dumbledore's man. Voldemort shoots the killing curse at Harry, the same time that Harry also shoots a spell. The spell rebounds, and Voldemort is finally killed once and for all, never to return.