Champagne terminology
In order to qualify as true champagne, the wine has to come from the Champagne region of France. Everything else, technically speaking, is just sparkling wine, although it may be very good sparkling wine.
There are different levels of dryness in champagne and sparkling wines, depending on the amount of sugar added at the end of the production process. They are labelled as follows:
Extra Brut: the very driest, with no added sugar.
Brut: very dry
Extra dry: dry to medium dry
Sec: getting sweeter...
Demi-sec: ...and sweeter
Doux: the sweetest. Often drunk as a dessert champagne.
A champagne may be either vintage or non-vintage. Vintage champagnes are produced in exceptionally good years, and so are less common and correspondingly more expensive. The wine is aged for three years before release, and the year is printed on the bottle. It will have a more complex and fuller flavour. Non-vintage champagne is made from a blend of grapes from different years. It may still be very good, and won't be so astronomically expensive.