A Target Swinger is a type of gravity moving target that is commonly used in shooting competitions and law enforcement training. Swinger Targets are often placed behind a wall or structure so they are only exposed to the shooter for very brief intervals as they swing back and forth. When set up in this configuration, they are often referred to as Bobber Targets because they "bob" in and out of sight.
Almost every USPSA match will include IPSC Swinger Targets in various configurations. Match designers utilize this style of target frequently because it is much more difficult for shooters to score well on a moving swinger target than a target placed on a stationary target stand.
The International Defensive Pistol Association also commonly uses IDPA Swingers in their competitions. This IDPA stage design template provides some useful suggestions for how the IDPA Swinging Targets can be used in a match.