Cask conditioning is a method of packaging and dispensing beer. This process was made famous and perfected by the British, prior to the advent of refrigeration and CO2 draft systems. After the primary fermentation is complete, the beer is put into a cask, sugar is added (primed), and the cask sealed. The ale is then allowed to sit for a few days at a warmish temperature. This enables a secondary fermentation to take place, resulting in the natural carbonation of the beer. The beer is then cooled to the low 50′s F.
To dispense, the cask can be placed directly on the bar and the beer poured out through a spigot, or it could be attached to a hand pump, also known as a beer engine. This device is clamped to the bar, and actually pumps the beer out of the cask, which is traditionally in the cellar. Alex Hall, of the Gotham Imbiber, wrote an excellent article on the process.
There are a few local bars that regularly serve cask ale, but because of its delicate nature and short shelf life, it is not always available. Pratt Street Alehouse and the Wharf Rat, both in Baltimore, almost always have cask ale. Max’s Taphouse and Metropolitan Coffee House and Wine bar, also in Baltimore, offer fresh casks every Thursday night. There are others, but they don’t seem to be as consistent as these four. Here is a link to help you find Cask Ale.
There is plenty more to write on this subject, but in the meantime, I encourage you to seek out cask ale. Forget about any of the “warm and flat” nonsense that you may have heard and give it a try. Cheers!