Subdivisions are land that is divided 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.

Subdivisions may also be for the purpose of commercial or industrial development, and the results vary from retail shopping malls with independently owned out parcels to industrial parks.

In the United States, the creation of a subdivision was often the first step toward the creation of a new incorporated township or city. Contemporary notions of subdivisions rely on the Lot and Block survey system, which became widely used in the 19th century as a means of addressing the expansion of cities into surrounding farmland. While this method of property identification was useful for purposes of conveyancing, it did not address the overall impacts of expansion and the need for a comprehensive approach to planning communities.

In the 1920s, the Coolidge administration formed the Advisory Committee on City Planning and Zoning, which undertook as its first task the publication of The Standard State Zoning Enabling Act in 1926, model enabling legislation for use by state legislatures. This was followed by publication of the Standard City Planning Enabling Act (SCPEA) in 1928. The SCPEA covered six subjects: (1) the organization and power of planning commissions, which was directed to prepare and adopt a master plan; (2) the content of the master plan; (3) provisions for a master street plan; (4) provisions for approval of all public improvements by the planning commission; (5) control of private subdivision of land; and (6) provisions for the creation of regional planning commissions.

The SCPEA included the following definition:

"Subdivision" means the division of a lot, tract, or parcel of land into two or more lots, plats, sites, or other divisions of land for the purpose, whether immediate or future, of sale or of building development. It includes resubdivision and, when appropriate to the context, relates to the process of subdividing or to the land or territory subdivided.

Attached to this definition was the following footnote:

for the purpose of sale or of building development: Every division of a piece of land into two or more lots, parcels or parts is, of course, a subdivision. The intention is to cover all subdivision of land where the immediate or ultimate purpose is that of selling the lots or building on them. The object of inserting a definition in the text of the act is to avoid the inclusion, within the planning commission's control, of such cases as a testator's dividing his property amongst his children, partners' dividing firm property amongst themselves on dissolution, or cases of that nature.