This is the biggest part of the instrument. It is hollow to allow the sound of the strings to reverberate.
This is where the strings attach at the bottom of the instrument. In this example the tailpiece also contains the fine tuners for small adjustments to string tension.
This retractable spike is used to support the base of the cello on the floor.
This is usually maple and gives the strings the necessary shape across the fingerboard to the bridge. An incorrectly placed bridge can place unnecessary stress on the instrument - it should be roughly where it is on the photograph, next to the arrows of the f holes.
These are used for large adjustments to string tension. Because the pegs are tapered, you'll need to push them inwards as you twist them to help them hold tune.