Lagering

A form of beer maturation on the yeast that usually lasts for several weeks, or sometimes months, at or near freezing temperatures. Lagering occurs after fermentation and before filtration and/or packaging of the beer.

Lagering tanks

Lagering traditionally is done to lagers (duh), but may sometimes also be done to ales such as Kolsch and Altbiers. 

Lagering alters the flavor of beer to produce a crisp and clean taste associated with lager beers. Lagering will also reduce protein haziness and promote beer stability.