A plat is a survey-based map showing the legal subdivision of land into lots, blocks, streets, easements, and similar features. Plats are recorded with the county or other land-records office and become the legal description of how the land is divided. Subdividing a parcel for development requires creating a new plat (or amending an existing one) and recording it through the local platting process.
For contractors, the plat is the authoritative source for lot boundaries, recorded easements, dedicated streets and rights-of-way, and similar legal features. Always verify the plat against the survey before site planning. The platting process for new subdivisions can take 6 to 18 months depending on jurisdiction and is typically the longest pre-construction step on greenfield development.