Akatsuki is a sand demon that resembles a raccoon. Gaara's mother bonds him with Akatsuki while he's still in the womb, and as Gaara grows, he learns to control more of the demon's power. In this respect, he has a lot in common with Naruto, who also is bound to a demon. Akatsuki both protects Gaara and torments him. Gaara rarely lets himself sleep because when he dreams, Akatsuki gnaws at his mind. This is why Gaara is always drawn with dark rings under his eyes.
Although Gaara is the son of his village's leader, the Kazekage, he's an outcast amongst his peers. The other children fear and despise him because of the demon, Akatsuki. His mother is dead. His father fears him. His only companion is his uncle, Yashamaru. When Gaara inadvertently kills someone at the age of 6, even Yashamaru turns on him, attempting an assassination. Gaara defends himself, killing his uncle in the process. After that, he does whatever it takes to survive, earning the name "Self Loving Carnage."
Like the other ninja in "Naruto," Gaara is both a skilled martial artist and a wielder of seemingly magical powers. His powers are derived from the demon, Akatsuki, which telepathically controls sand. Using these powers, Gaara unconsciously surrounds himself with a shield of sand, and by the age of 11, he has never been cut or injured. In addition to defending himself, Gaara uses sand to crush his opponents. He has no qualms about killing people, and he often goes out of his way to mingle blood and sand.
When Gaara first appears in the "Naruto" series, he's psychotic and selfish. After Naruto defeats him, Gaara begins to question the way he lives. Up until then, he'd only fought for himself. Naruto won by fighting on behalf of his friends, however, and that gave him strength. Gaara realizes that life has more meaning when it's lived for the sake of others, and over the ensuing episodes, he slowly matures. By the end of the first "Naruto" series, he becomes the new Kazekage of his village, leading them with both compassion and wisdom.
In the second "Naruto" series, Gaara's village is attacked by Deidara. As the leader of his village, he rushes to defend it. Despite some initial success, Deidara ultimately defeats him and takes Gaara to a secret laboratory and extracts the demon Akatsuki. In the process, Gaara dies. Later, he's revived by the village sage, Chiyo. Without Akatsuki, however, he no longer has the extensive sand-bending power he once did.