Craft beer is a term used by many beer enthusiasts, especially in the United States, to describe beer designed to appeal to the beer enthusiast rather than the mass market.
In the early days of what is now often called the 'craft beer revolution in the United States, the exciting new beer was usually being brewed by very small breweries, and it was generally called microbrewed or microbrewery beer. But as the segment grew, the term microbrewery became less relevant.
When Sam Calagione founded Dogfish Head in 1995, he chose to call it a "craft brewery" rather than a "microbrewery" because he wanted to be defined by quality rather than size.
Craft beer encompasses not just larger brewers with wide distribution, such as Sam Adams (according to some) and Anchor Brewing, and quality imported beers from other countries with no equivalent to the American microbrewery, but also quality beers brewed by joint-venture or captive breweries run by large brewers of mass-market beer.