I'm trying to narrow down my bike search. I've been riding several times a week for over a decade on the same inexpensive hybrid bike. I've been visiting local bike shops looking for my first road bike. I've been reading several forums religiously. I've been talking to many cyclists. I've been reading books and articles. The bikes that have been recommended to me by many people are the Trek Madone 4.5, Specialized Roubaix Elite, Cannondale CAAD 9, Cannondale Synapse. I've been able to spin so far in the shop on the Cannondales. A few bike shop owners have told me that test rides are not as important as "fit". So, not to be dense, but what is "fit"? How do I know which brand or which individual bike "fits" me? I understand that I should be measured, a frame selected, and standard riding position achieved, but I suspect that this is not totally what people mean, and no one as of yet has been willing to concisely explain this to me, so I am stuck as to how I should proceed.

Can anyone help?