That Nashbar steel CX looks like a great deal. 105 bike for $800!

OP, as far as component terms go, look up the top component makers, Campagnolo, Shimano and SRAM and you'll see varying groups of components with different names. Each manufacturer has varying levels of group sets with the top of the line having the most advanced technology available. In your price range and bike type you'll be looking at Shimano and SRAM for the most part.

For Shimano the groups from top of the line down are: Dura-Ace, Ultegra, 105, Tiagra, Sora, 2300, 2200. The higher up the list, the higher the price of the bike. Shimano 105 is a very respectable groupset. I have a bike with 105 that is 9 years old and I've replaced chain and cassette and that's it.

I'm really thinking I might need to buy that Nashbar bike as a winter commuter myself.