What is the spacecraft?
The spacecraft is the protective "spaceship" that enables the precious cargo (that is, the rover!) to travel between Earth and Mars. It is separate from the launch vehicle that carries the spacecraft and the rover outside of Earth's atmosphere and gravitational pull. The spacecraft includes the mechanical units that safely carry and maneuver the rover through the Martian atmosphere to a landing on Mars.
Based largely on the successful Mars Science Laboratory mission, the spacecraft design would consist of three major parts:
Cruise Stage: Configuration for travel between Earth and Mars that includes an aeroshell (backshell with heatshield) in which the rover and its landing system are enclosed.
Entry, Descent, and Landing System: Configuration for entry into the Martian atmosphere. Includes the aeroshell, parachute, descent vehicle, and structure for a skycrane maneuver that would lower the rover to the Martian surface on tethers.
Rover: A wheeled vehicle with science instruments for discoveries on the Martian surface.