People often use the terms land, real estate, and real property interchangeably, but there are some subtle distinctions. Land refers to the earth's surface down to the center of the earth and upward to the airspace above, including the trees, minerals, and water. Real estate is the land, plus any permanent man-made additions, such as houses and other buildings. Real property—one of the two main classifications of property—is the interests, benefits and rights inherent in the ownership of real estate. Broadly speaking, real estate includes the physical surface of the land, what lies above and below it, what is permanently attached to it, plus all the rights of ownership—including the right to possess, sell, lease, and enjoy the land.