Road vs TT vs Track

[dain2772]

I know this is a very basic question, but what are the differences between the different 'Road' bikes?

I specifically ask this in reference to the tour de france, in that they use different bikes for the TT. Why not use a more aerodynamic bike for the other stages as well, surely there would be benefits on the flats and downhills? And are there benefits with the different types of bars?

 

[fauxpas]

The time trial bikes are not good at manouvering or hill climbing. The fork angle makes them manouver not as good... the geometry and gearing make them not good at hills... Solid aero wheels maybe good for TT course, but not in the blustery mountains...