Original: Unable to visit his children, Cobb is offered a chance to regain his old life in exchange for an almost impossible task: "inception", the planting of an idea into a target's subconscious.
Simplified: Cobb has two children but can not visit them. He is offered a chance to go back to his children in exchange for one last job: performing inception, which is planting a new idea, into the mind of his client's main business competitor.