In terms of types of beer, strong beer is a beer with an original gravity of at least 16° Plato, also resulting in a higher alcohol content of minimum 6.5% vol.
Because of the high original gravity and alcohol content, strong beers tend to have a strong taste. A very distinctive, often sweet malty body coupled with a higher throat-warming alcohol content can lead to a powerful beer experience - as the name suggests.
Strong beers include lots of typical German types of beer such as Bockbier, Doppelbock and Weizenbock, as well as international beers such as Barley Wine and Imperial Stout.
An example of a Steamworks strong beer is Imperial Red Ale, which, as the epithet implies, is brewed as a strong beer.