A "20 gauge" refers to a specific size of shotgun, which is a type of firearm designed to shoot shells filled with pellets or slugs. The gauge number indicates the diameter of the shotgun barrel; in this case, a 20 gauge barrel has a diameter that allows for 20 lead balls of the same diameter to weigh one pound. This makes the 20 gauge lighter and less powerful than larger gauges, such as the 12 gauge, making it a popular choice for small game hunting and sport shooting. The 20 gauge shotgun is often favored by beginners and those who prefer a lighter firearm due to its manageable recoil. It is commonly used for hunting birds, such as quail and pheasant, as well as for clay target shooting. Many manufacturers produce a variety of shotgun shells and firearms in this gauge, providing options for different shooting needs and preferences.