Darth Maul was an Iridonian (or Zabrak), born on Iridonia. At an early age he was trained as a Jedi, but was kidnapped by Darth Sidious, who conditioned him to forget everything he had learned from the Jedi. He then began to teach him the ways of the Dark Side. Maul had absolutely no memories of his homeworld of Iridonia and was incapable of feeling emotions outside of bloodlust and rage. Sidious turned him into a brutal killing machine and a weapon of pure hatred, severely punishing any show of fear or mercy. Maul is described as the ultimate tool of the dark side, with Sith tattoos covering his entire body. The reason that Maul was Sidious' apprentice is because of the martial powers of the Zabraks and how they'd hire themselves to the Sith.
Maul was pitted against a Force Sensitive Drovian called Silus, and Sidious sent him to an unknown planet in the Outer Rim. Maul delivered Silus his Masters message which turned out to be Sidious offering Silus the chance to become his new apprentice if he could kill Darth Maul. An energy nullifier denied Maul the use of his Lightsaber and the two fought with Force Powers and hand to hand combat, with Maul having self-doubts about himself after Sidious saying that he'd replace him, his focus lost. Eventually he called upon all of his rage and he used the Force to overload the field, and killed Silus with his Lightsaber.
Maul were abandoned by Sidious on a deserted Outer Rim world. There he was forced to survive alone for a month with hordes of Assassin Droids hunting him. His master then returned and challenged him to a duel. In his weakened state, Maul quickly lost. Sidious told him that he had failed and would soon be replaced. Enraged, Maul attacked his master, nearly defeating him. When his energy finally runs out, he submitted and prepared himself to die. However, he were met with Sidious' approval. By actually wanting to kill his Master, Maul had passed the final test. He was proclaimed Darth Maul, Dark Lord of the Sith, and taken to his new home on Coruscant.
Darth Maul trained to be a master of lightsaber combat, as well as acrobatics and hand-to-hand combat. Maul crafted a twin-bladed lightsaber, with ancient plans from a Sith holocron. Sidious gave Maul, funds, schematics, and a secret facility on Coruscant in which he could work. There he constructed his speeder bike, Bloodfin, and his Dark Eye probes. He were also given a powerful Sith Infiltrator named Scimitar, which has it's own cloaking field generator.
Before The Phantom Menace Maul was sent on many assassination missions of politicians, warlords, crime bosses and merchants.
Star Wars Episode 1: The Phantom Menace
Darth Maul is sent to Tatooine to capture Queen Padme Amidala and kill Obi-Wan Kenobi and Qui-Gon Jinn, but failed. He later tracked them down to Naboo where he ignored the queen and attacked the two Jedi. A climactic lightsaber battle ensued, with Maul holding the two Jedi at bay with his double-bladed lightsaber. When Obi-Wan is seperated from Qui-Gon and Maul by a laser wall. He temporally stuns Qui-Gon with a blow to the head, and stabs him, mortally wounding him. It could just have happened because Qui-Gon was tiring through his use of Ataru, and in the confined space Qui-Gon was also deprived of most of his defenses while Darth Maul had youth and strength on his side. The laser wall receded and Obi-Wan attacked Maul in an intense rage. He cuts Maul's lightsaber in half, but Maul Force-pushed him into a pit. Obi-Wan managed to hold onto a pipe, and Maul started to taunt him. Obi-Wan calmed himself and reaches out to the Force. He made a miraculous jump out of the pit, simultaneously pulling Qui-Gon's lightsaber into his hand. The stunned Maul barely had time to grunt as Obi-Wan's lightsaber cut Maul in half and he tumbled down the chute in two pieces.
Darth Maul survived the battle and held on to his anger. He quit being a Sith and decided to be the leader of Crimson Dawn, with Qi'ra and Dryden Vos as his allies.
Maul appears a a playable Sith "hero" character in Star Wars: Battlefront II. Maul also appears as a boss in The Force Unleashed, when PROXY takes his form on Imperial Raxus Prime. This is not technically Maul, but for all gameplay intents and purposes he is.