Darth Maul is the Sith Apprentice of Darth Sidious, also known as Senator Palpatine of Naboo (later to become Emperor Palpatine). In the Star Wars universe, the Sith are an ancient sect of warriors dedicated to the Dark Side of the Force. The Jedi believed they had been hunted to extinction, but the Sith survived. Passing on their evil craft until they could get their revenge led to the Dark Lord Darth Sidious, who took Darth Maul as his apprentice.
Darth Maul is about 5 feet 9 inches tall with horns on his head that put him at about 6 feet tall. He generally wears a black cloak over his Sith Robes. His skin is completely covered in red and black tattoos, which signify his devotion to the Sith Order. (The tattoos are all Sith Markings). He has yellow eyes and jagged, pointed teeth.
The character is first seen in Star Wars Episode 1. Darth Sidious sends him to track and capture Queen Amidala of the Naboo, who escaped her planet after an invasion orchestrated by Sidious. Darth Maul tracks her to Tatooine where she is under the protection of Jedi Master Qui-Gon Jinn and his Jedi Apprentice, Obi-Wan Kenobi. Maul and Qui-Gon fight in the Tatooine desert which results in a narrowly attained draw by the Jedi. This leads them to the conclusion that the Sith have returned to the galaxy.
Darth Maul follows them back to Naboo when the Queen decides to attempt to take back her planet. Maul and the Jedi meet for 1 final duel, where Maul, brandishing the first-ever seen double-bladed light saber in the movies, defeats and kills Qui-Gon while Obi-Wan watches. Maul and Obi-Wan duel, which almost results in Obi-Wan's loss, but he narrowly defeats Maul, resulting in Darth Sidious having to choose a new apprentice.
The Extended Star Wars Universe of Books and Comics has sought to explain and flesh out a character, that while popular, didn't get much back story in the films. Most of these stories have attempted to shed some light on the character's mysterious background. The novel, "Darth Maul: Shadow Hunter" explains how he was kidnapped as a child and his extreme training to become a Sith (see link in Resources). In the comic book "Resurrection," from Star Wars Tales #9, fans were given a match between Darth Maul and Darth Vader to determine who was the stronger Sith Lord. Even though this character was limited to 1 movie, it has lasted in the psyche of the Star Wars fandom.
Originally, Darth Maul was to look a bit like Darth Vader to draw a parallel between the older trilogy and the prequels, but that concept was discarded quickly. Iain McCraig, Maul's concept artist finally settled on a menacing tattooed look, Maul's final look. He was portrayed by Ray Park and voiced by Peter Serafinowicz.