There are four broad types of property: land, immovable property, personal property and intellectual property. Real property (also called real estate or realty) means the combination of land and improvements. Under a property tax system, the government requires and/or performs an appraisal of the monetary value of each property. A tax is assessed based on that value. Forms of property tax used vary among countries and jurisdictions. Real property is often taxed based on its classification. Classification is the grouping of properties based on similar use. 