Champagne is the northern most wine region in France, and because of its continental climate it has cool summers and very cold winters. This produces wines which are very light and high in acidity, not particularly pleasant as still wines but perfect as the base of a sparkling wine. They are blended and bottled with added sugar and yeast which starts a second fermentation. This produces carbon dioxide which is trapped in the bottle forming the sparkle. The contact with the yeast in bottle also adds the complex biscuity brioche character of Champagne.
There are several styles of Champagne, the most common being non-vintage. These are blended from the three Champagne grapes (Chardonnay, Pinot Noir and Pinot Meurnier) into a consistent house style, using reserve wines held back from previous vintages to even out vintage variation and achieve consistency.
Vintage Champagnes are produced solely from the grapes of one year and are much more variable, expressing the character of the year in which they were made as well as the 'house' style; they are often only made in better years. Occasionally Blanc de Blanc or Blanc de Noir wines are made from purely white or black grapes respectively, while rosés are made from either adding still red wine or allowing some colour to enter the wine from skin contact.
Most Champagnes which enter Britain are Brut, a dry style where a relatively low 'dosage' of sugar is added when the wine is finally sealed. However, there are also the extremely dry Ultra Brut, and Sec, Demi-Sec and Rich (Doux) styles in ascending order of sweetness.
It was the cool winters of Champagne which originally caused the sparkle in the wine, as fermentation would stop in the cold and wines would be bottled, fermentation starting again when it became warmer. This created a light sparkle which was very popular but had the unfortunate effect of causing most of the bottles produced to explode!
It was only in 1662 when the wine was introduced to London by an exiled aristocrat that stronger bottles were developed and the drink took off in the London café scene of the time, yet even so over half of the tiny production (less than 1,000 cases were produced a year) survived.
It was only in the early 19th century that a full industry started. It was Madame (Veuve) Clicquot who introduced the modern system of deliberately inducing a second fermentation by adding sugar and yeast which is then removed, and her innovations attracted entrepreneurs such as Messrs Bollinger, Krug and Roederer among others to the area.
Incidentally, Dom Perignon, the man who according to folklore 'invented' Champagne, did study the sparkle in wine... but only with a view to preventing it!