It is exactly as it sounds, its people and teams cooking barbecue in some kind of competition structure. There are varying degrees of rules and judging processes depending on the contest. Types of contest are varied but the most popular structure is the "low and slow" format sometimes known as Master Series.
Low and Slow or Master Series events follow an established four round structure, usually of chicken, pork ribs, pork shoulder and beef brisket. These are the standards of American barbecue. Variations on this include Kosher, where pork is swapped for Kosher meats including beef ribs. More info can be found on our page here.
Essentially though, a barbecue contest can and often is very varied. Individual organisers will often create bespoke rounds and criteria. Several organisations exist to provide local and international structure, but ultimately many contests design their own structure.
There are a few organisations large and small that will provide governance and structure to barbecue contests. The biggest is KSBS (Kansas City Barbecue Society). As well as sanctioning many Master Series contests across the USA, they provide their competition structure to some of the biggest and most prestigious contests in the UK and Europe. Many teams will focus on KCBS contests because of the opportunities it presents for invitational events across the world and to compare with teams across the world.
Other sanctioning bodies for Low and Slow events include IBQN (International Barbeque Network), while other types of contest such at steak cooking are sanctioned by organisations such at SCA (Steak Cookoff Association). Other organisations exist, some providing sanctioning others not. More information can be found in the "Organisations" section of this site.