The Imperium of Man encompasses innumerable planets, classified and registered by the Adeptus Adminstratum, based mainly on their tithes and inhabitability. 

Hive Worlds: typically, home to many Hive cities, immense urban territories with billions of inhabitants, the main tithe here is the populations itself. Prone to high gang activities and mutant anomalies.

Feudal Worlds: mainly rediscovered planets, whose inhabitants are on a lower technology level, mostly feudal.

Feral Worlds: wild, mostly inhabited worlds on barbaric advancement level.

Forge Worlds: these planets are dedicated to the Adeptus Mechanicus, making huge industrial stations. First and greatest of them is Mars, the home of the tech-priests.

Agri Worlds: worlds with the sole purpose of producing nourishment for the immense population of the Imperium, very often the residents almost kept as slaves on their own home planet, but the quotas must be met, for the legions must be fed. 

Mining Worlds: rich in strategic resources of some kind, the population of these planets often consists of prisoners and penal workers, accordingly the sole aim of their existence is to extract the riches of the planet, their lives are invaluable. 

Fortress Worlds: bastions of the imperial defence lines, these are extremely well defended planets, stationing many Imperial Guard regiments and a huge number of Imperial Navy vessels. The most famous Fortress World is Cadia. 

Shrine Worlds: sanctuaries of faith and piety, these planets are dedicated to the Ecclesiarchy, often birthplaces of saints, sites miracles or holy visitations. Monumental cathedrals, shrines and reliquaries stretch trough the surface, and sometimes the home fortresses of Adepta Sororitas Orders. 

Death Worlds: these are either devastated planets that cannot support life any longer, or worlds so dangerous that life on them is nigh impossible.