Background
I find myself looking into buying a decent bike for the first time in my life (previous bikes having all been gifts or walmart specials). As such, I find myself trying to figure out what a lot of the terms, names, and numbers mean. Fork materials? Tire styles/sizes? Derailleur brands? StackExchange sites are great for answering specific question, but aren't entirely ideal for people who don't yet know enough to know what they need to ask. The unknown unknowns, as it were.
Question
What are some good resources or primers for someone looking for a general overview of the decisions to be made when purchasing a bike, and the various tradeoffs associated with them?
I'm thinking of buying a bike and don't even know where to start. What are the key things to look for when buying a bike?