What is an estate? what estates existed in medieval society.

An estate is a social community whose members are different from other members of society in their legal, social status. The estate principle of dividing society was the basis for building a social hierarchy in medieval European society. There were three main estates: aristocrats, priests, commoners (communes), however, in later stages in some countries, two more estates were distinguished: the bourgeois (industrialists) and the peasants.