Champagne is both a wine region and a method of winemaking. The wines come from the northern most vineyards in France - and the name conjures an image like no other.
An 18th Century Benedictine monk named Dom Perignon was the first to clearly document that the cold winters stopped 'still' wine fermenting, then as the climate warmed up, fermentation would start again.
This second fermentation produced CO2 (carbon dioxide) inside the bottle, meaning the wines had a sparkle that was quite appealing. Unfortunately, the strength of this secondary fermentation frequently exploded the flimsy bottles of the day. Extra thick bottles were made in the UK - and as they say the rest is history.

 

Champagne can be made from 3 grape varietals: Chardonnay, and two black skinned grapes, Pinot Noir and Pinot Meunier. Each plays their own unique part in the blend. Being a white wine from red grapes, this is a delicate process.
Champagne is made to a strictly controlled process called 'Methode Champenoise'. The grapes are pressed and fermented to make a dry still wine. Blending of all the different grapes and parcels to make the house style follows. Then a blend of sugar and yeast is added and the wine is bottled and temporarily capped with a crown cap. Secondary fermentation, the CO2 that is lost to the air when making a still wine is now captured inside the bottle. This process leaves sediment (dead yeast cells) that is extracted through a process of 'riddling'. The bottles are progressively turned upside down until all the sediment is collected in the neck. The necks are then frozen and the sediment is 'disgorged'.
After this phase, the winemaker may decide to add a natural sugar liqueur to determine the final sweetness of the wine. Champagnes typically range from dry, 'Brut', to slightly sweet, 'Demi-Sec'. Finally the wine is corked, caged and labeled. Law requires 15 months ageing for non-vintage Champagne, a few top houses age their wine longer to build greater complexity and depth - e.g. Pol Roger Brut Reserve NV is matured for 3 years. NV Champagne generally doesn't benefit from further ageing after purchase, as the winemaker has done all the hard work before release, to make sure it is balanced and ready to drink when you buy it.