Private property is a concept used in law, which is defined as a certain type of thing which is owned and controlled by an individual or a group separate from the state. Private property differs from public property, where such property belongs to all. That way, a person may own a car, but the park in the city is only administered by the city, and belongs to all people (or to no one at all).
Different schools of thought have different ideas of how private property should be handled.
For instance, according to capitalism, private property is needed so that a society can work as it should. That way, trade can only be done using private property. As a secondary example, private property in Marxist theory refers to the means of production, such as mines, factories, burger joints, and so on. These are things communists want to be democratically owned by workers. This is different from personal property, such as a toothbrush.