What is the part of the space shuttle that carries the crew and payload?

The Orbiters carry the Astronauts (Command Crew and Mission Specialists) in the main Crew Cabin, which is a separate compartment and highly survivable in an accident in Earth atmophere. Several of the Challenger crew were known to have survived the initial breakup of the Orbiter after the SRB/MFT explosion, only dying after impact with the water.

All mission equipment and satellites (tools, protective enclosures (MOPE, SOPE, etc.) as well as experiments and satellites are carried in the Shuttle Payload Bay. All items are processed in clean rooms, and a huge mobile clean room is rolled into place over the payload bay to assemble and install all items in preparation for an upcoming launch. The process usually takes around a month.

If you click on my Supervisor bio link, you can see pictures of various stages of the Hubble Space Telescope NICMOS Cryocooler and Capillary Pumped Loop panel in various stages of production before being loaded on a shuttle for the Hubble Orbital Systems Test, aboard the flight that carried John Glenn back to space in 1999.