Champagne is a single Appellation d'Origine Contrôlée, meaning only sparkling wine produced in its namesake region and adhering to defined standards can be called Champagne.
Grapes must be the white Chardonnay, or the red Pinot Noir or Pinot Meunier (a few very rare other grapes that were historically important are allowed, but very unusual). Champagnes made exclusively from Chardonnay are known as blanc de blancs, and those exclusively from the red grapes as blanc de noirs.
Champagne's sugar content varies. The sweetest level is doux (meaning sweet), proceeding in order of increasing dryness to demi-sec (half-dry), sec (dry), extra sec (extra dry), brut (almost completely dry), and extra brut / brut nature / brut zero (no additional sugar, sometimes ferociously dry).
There are sparkling wines made all over the world, and many use special terms to define their own sparkling wines: Spain uses Cava, Italy calls it spumante, and South Africa uses Cap Classique. A sparkling wine made from Muscat grapes in Italy uses the DOCG Asti. In Germany, Sekt is a common sparkling wine. Other regions of France are forbidden to use the name Champagne; for example, wine-makers in Burgundy and Alsace produce Crémant.