What is "guest beer"?

Guest beer is a term used to describe a beer that is not a regular part of a bar or pub's beer selection, but is instead brought in as a special offering or feature. Guest beers are typically chosen by the establishment's management based on factors such as the popularity of the brewery or the style of beer, and are often rotated on a regular basis to provide variety for regular customers and attract new ones. The guest beer may be from a local or regional brewery, or may be from a well-known national or international brand. Guest beers are often advertised on a chalkboard or other display, and may be offered in different sizes or at different prices than the regular beer selection.