Champagne is a region located approximately 90 miles northeast of Paris, France. While vines have been producing wine in this region since the Roman era, it is only in the past couple hundred years that they began producing it in the method associated with it today (i.e. bubbly).
Within this region chalk and limestone soils dominate which result in wines high in acidity (a KEY component to making good sparkling wine). Its northerly location, about as north as grapes can ripen, which allows for higher acidity and lower alcohol levels (also very important for quality sparkling wine).
Without getting too technical for this overview, it is basically the soils, vineyard conditions, and regulated method of production (described next), that all affect the overall product.