Here's a little blurb from Wikipedia:
Emmental or Emmentaler is a cheese from Switzerland. It is sometimes known as Swiss cheese in North America, Australia and New Zealand, although Swiss cheese does not always imply Emmentaler.
The cheese originally comes from the Emme valley in the canton of Bern. Unlike some other cheese varieties, the denomination "Emmentaler" was not protected ("Emmentaler Switzerland" is, though). Hence, Emmentaler of other origin, especially from France and Bavaria, is widely available. Even Finland is an exporter of Emmentaler cheese.
Emmentaler is a yellow, medium-hard cheese, with characteristic large holes. It has a piquant, but not really sharp taste. Three types of bacteria are used in the production of Emmentaler: Streptococcus thermophilus, Lactobacillus, and Propionibacter shermani. In the late stage of cheese production, P. shermani consumes the lactic acid excreted by the other bacteria, and releases carbon dioxide gas, which slowly forms the bubbles that make holes.