Sour style beers originally were fermented in barrels and would take a relatively long time to mature. Styles such as gueuze (an unfruited sparkling form of lambic) is created by blending one or more lambics of different ages together in a bottle. The younger lambic provides sugars which are used to help the beer ferment in the bottle. Barrel aged sours develop an array of flavors over time and many are complex and unique. A more recent souring method, kettle souring, decreases the time it takes to sour a beer. This method starts out much like brewing any other beer style.
Hang around the craft beer industry long enough and you are going to run into people using the word Cicerone (pronounced "sis-uh-rohn"). It comes directly from the Cicerone Certification Program which was founded by beer industry veteran Ray Daniels.