May all your pains by Champagne...the secret is in the bubbles

Traditionally, Champagne has two fermentations, one as a dry white wine in the same way we would make Riesling or Sauvignon Blanc. The secondary fermentation occurs in the bottle and the carbon dioxide released from the Fermentation produces the bubbles in the bubbly!
There are four distinct methods to making sparkling wine, each of them moving up in price, quality and enjoyment to the wine lover.

In order of Quality & Price parameters:

Carbonated

The wine undergoes a primary ferment, generally in stainless steel with some old wine stocks added for complexity. As it is being bottled down the bottling line gased carbon dioxide is added which produces the bubbles. Using this process from harvest to finished product is about 6-8 weeks.
This process is similar to that used in soft drink production and produces big bubbles that dissipate quickly.
Sparkling Wines produced this way are on the less expensive end of the scale.

Pressure Tank Ferment
Primary fermentation occurs in stainless steel and/or old oak barrels, older wine stocks are blended for complexity. It all goes into a pressure tank of up to 10,000 litres. The secondary fermentation occurs in the tank taking 1 month. Hence, natural Carbon dioxide in the wine and the wines are then bottled.

This process takes a minimum of 6 months.
This method produces smaller, longer-lasting bubbles and is used in Processco production. These Sparkling wines are delicate and light.

Fermented in bottle
Primary fermentation occurs as per the earlier methods, the secondary ferment occurs in individual heavy weight glass bottles. Extra yeast and sugar is generally added to each bottle to kick off the secondary ferment. They will ferment in the bottle for 12-18 months producing natural Carbon Dioxide. All the bottles will then be opened and poured to tank. They are then filtered and bottled.

Once again the bubbles are more refined and the wine more complex.

The Traditional Method or Methode Champenoise

This means “Fermented in this bottle”. The primary ferment occurs in old French barrels, the wine is then transferred to heavy weight sparkling under crown seal. It is transferred on leaves with solids to allow the secondary ferment to occur. The secondary ferment for Method Champenoise takes a minimum of 12-18 months.
The wine can sit under crown seal for tens of years protecting the precious wine.
When the wines are ready to be consumed they go to the riddling racks so that all the solids can settle in the neck of the bottle. Then disgorging process involves freezing the necks of the bottle with liquid nitrogen, crown seals are popped and leaves and solids are shot out with a small amount of liquor made from the base wine is added to each bottle to top it up. Corks, wire nets, and labels are all added to finalise the process.

So Method Chapenoise takes 2 years or more to make. Once disgorged the wine should be drunk within then 9-12 months. Champagne connoisseurs will order their Vintage from the Champagne house and have it disgorged to order.
Gorgeous creamy complex Champagne's and Sparklings are made this way and are of the more expensive.

For examples of these variations visit
http://www.clubwinedirect.com.au/wine-type/champagne
or
http://www.clubwinedirect.com.au/wine-type/sparkling-wine

Info from Randal Tomich
Ref:http://en.wikipedia.org/wiki/Méthode_champenoise#Traditional_method