Cask conditioned beer, often referred to as 'real ale,' is brewed from only traditional ingredients and allowed to mature naturally. Casks, also called a firkin, are filled by many local craft brewers.
The unfiltered, unpasteurized beer still contains live yeast, which continues conditioning the beer in the cask (known as "secondary fermentation"); this process creates a gentle, natural CO2 carbonation and allows malt and hop flavors to develop, resulting in a richer tasting beer with more character than standard keg "brewery-conditioned" beers.
Real ale is always served without any extraneous gas, usually by manually pulling it up from the cellar with a hand pump, also known as a "beer engine". This is the traditional way of serving beer; only a few decades ago did filtered, pasteurized, chilled beer dispensed with gas become normal.
It's simple to add cask conditioned beers to any establishment. Offer your guests more choice. Dispense a pint of cask conditioned "real ale" and enjoy the freshest expression of the brewers art!