Generally, there are three manufacturers that make "drive train" components for bikes. All three make super-high race quality components, down to entry-level (some more entry-level than others). Below I listed the order for each from highest to lowest price. The further down the list the less you'll pay for a bike.
Beyond this there are many manufacturers that make specific components that may be substituted for any of these. In particular with cranks, you'll often see a different brand substituted in for a multitude of reasons. But if you look at a bike you can kind of judge it by the components - it will either be mostly Tiagra, or it could be a mix of Tiagra and 105 (for instance). Since 105 is a more expensive group, either the price of the bike will be more, or another component has been downgraded to offset the cost of the 105.
Shimano: Dura Ace >> Ultegra >> 105 >> Tiogra >> Sora
SRAM: Red >> Force >> Rival
Campagnolo: Super Record >> Record >> Chorus >> Athena >> Centaur >> Veloce
Tubing is harder to explain because every company's marketing department makes up names to differentiate it's tube sets from other companies. There's no standard to any of the naming, and the names can be misleading.
Generally frame come in either carbon fiber, aluminum, or steel. All three can be used to make great bikes. Each has their strong points and each their weaknesses - none is particularly better than the other. Instead of trying to learn all of the differences, it's better to concentrate on how a particular bike rides and if you're comfortable on it. Pick the bike that you want based on how it feels when you ride it.
