Small dogs like terriers are sent into badger setts by the baiter,  typically with GPS trackers fitted to their collars. If the dog/s find a badger there will be a standoff and the dogs will make the baiter above ground aware by barking. The badger will either come out of the sett to escape the dog or the sett will be dug into and the badger dragged out. Larger dogs may then be let loose on the badger or the badger may be bagged and taken away. Badger baiting and sett digging are illegal, and the harm caused to the dogs - many of are badly injured - breaches the Animal Welfare Act (2006). Baiters are extremely violent. DO NOT approach them, but record what details you can about location, numbers of people involved, what dogs they have, any vehicle registration details, and call the Police as soon as it is safe to do so.