Subdivisions are the act of dividing land into pieces that are easier to sell or otherwise develop, usually via a plat. The former single piece as a whole is then known as a subdivision. Subdivisions may be simple, involving only a single seller and buyer, or complex, involving large tracts of land divided into many smaller parcels. If it is used for housing it is typically known as a housing subdivision or housing development, although some developers tend to call these areas communities.

In the United States, a plat (plan) is a cadastral map, drawn to scale, showing the divisions of a piece of land. United States General Land Office surveyors drafted township plats of Public Lands Surveys to show the distance and bearing between section corners, sometimes including topographic or vegetation information. City, town or village plats show subdivisions broken into blocks with streets and alleys. Further refinement often splits blocks into individual lots, usually for the purpose of selling the described lots; this has become known as subdivision.