A kingdom is a state or country ruled by a king or a queen. In Warcraft, however, the term is sometimes used in a more broader sense to serve as a synonym for "state" or "country" - the magocracy of Dalaran, the state of Kul Tiras and the city-state of Theramore have all been referred to as kingdoms despite not being ruled by royalty.
The two great remaining kingdoms of Azeroth are Ironforge and Stormwind. Other surviving human kingdoms include Gilneas, Stromgarde and Kul Tiras, while Lordaeron and Alterac have been destroyed as political entities.
Other types of government
The shielded city-state of Dalaran is ruled by a group of mages from the Kirin Tor called the Council of Six, under a system referred to as a magocracy. The orcs, trolls, tauren, and various other races are ruled by a clan-based or tribal system, while the night elves share power between the leaders of their two main religious groups, the followers of Elune and the druids. The gnomish survivors of Gnomeregan are led by an elected official called the High Tinker although they were previously a monarchy.