This is one of the three components needed to create the Mars Science Laboratory Sky Crane. The other components are the Curiosity Rover MOC-0271 and the Sky Crane Stand MOC-0287. The Descent Stage is the vehicle that lowered Curiosity on a set of cables down to a safe and soft landing inside of Gale Crater on Mars. Once on the ground, the cables were cut and the Descent Stage flew off and intentionally crashed a safe distance away from the rover.
This model is more fragile and complex than the other components. Caution and patience is advised.