The immersive experience of Avatar would be enough on its own. That you are taken into a world where you essentially take part in the journey and evolution of a hero that deals with a supreme conflict just makes this film even more worth experiencing in an IMAX theatre.
The story follows Jake Sully (Sam Worthington), a paraplegic war veteran who is asked to participate in a high level program run by corporate and military strategists after his brother dies. Sully accepts and travels light years away to the planet of Pandora.
Humans cannot breathe the air on Pandora but through an Avatar Program they link to an avatar which is a hybrid of the indigenous people of Pandora that happen to have features of the individuals they are linked to.
Ultimately, Sully is offered the job because he is a genetic match for an expensive avatar that was designed for his brother. He signs up to help scientists learn about the indigenous people of Pandora, the Na'vi.
The scientists inform Sully that linking to his own avatar will give him the ability to walk again, an experience that becomes quite liberating.
Scientists carry out a mission designed to figure out why Na'vi/human relations are so tumultuous, a corporate-military management corporation ultimately oversees the scientific project.
The project exists, for the most part, because it may yield information that can help the Resources Development Organization gain access to the planet's natural resource, Unobtanium, which the corporation can use to save a dying planet Earth from its current energy crisis.