Originally Kellerbier (literal translation cellar beer) referred to any lager beer being matured in the caves or cellars below the brewery, known for to be a strong beer and destined to last the summer (Sommerbier). But when refrigeration came into use, the term came to describe specialty beers that were served young, straight from the cellar. Overall it has body and creamy texture due to the suspended yeast, and an additional yeast character, with some by-products not often found in well-aged German beers.
*Source: Beer Judge Certification Program (BJCP) - Beer Style Guidelines
