# Property data glossary

> Plain-English definitions of the terms used in US parcel, tax assessor, deed, permit and zoning records.

Source: https://www.parceled.ai/glossary  
Publisher: Parceled (https://www.parceled.ai)  
Updated: 2026-10-06

Property records use their own vocabulary. This glossary defines the terms you will meet in US parcel, tax assessor, deed, permit and zoning data, from APN and situs address to assessed value, mill levy, setback and nonconforming use, in plain English.

## Terms

**Parcel**: A piece of land that the county records and taxes as one unit, with one owner of record and one parcel number.

**APN (assessor's parcel number)**: The county's unique ID for a parcel. Also called parcel ID, PIN, tax ID or folio. See [what is an APN](https://www.parceled.ai/guides/what-is-a-parcel-number-apn).

**Situs address**: The physical address of the property itself, as opposed to the owner's mailing address.

**Owner mailing address**: Where the county sends the tax bill. When it differs from the situs address, the property is often rented or a second home.

**Assessed value**: The value property taxes are calculated on. Often a state-set percentage of market value.

**Market value**: The assessor's estimate of what the property would sell for on the valuation date.

**Mill levy (millage rate)**: The property tax rate, expressed in dollars per $1,000 of assessed value.

**Assessment roll**: The annual list of every parcel in a jurisdiction with its owner and assessed value.

**Recorder (register of deeds)**: The county office that records deeds, mortgages and liens.

**Deed**: The recorded document that transfers ownership of real property.

**Plat**: A recorded map that divides land into lots, blocks and streets.

**FIPS code**: The federal numeric code for a state (2 digits) and county (3 digits); together they uniquely identify a county, e.g. 08031 for Denver.

**Zoning district**: An area where the local zoning code sets permitted uses and building rules, labeled with a code such as R-1 or C-2.

**Overlay district**: An additional zoning layer (historic, flood, airport) that adds rules on top of the base district.

**Setback**: The minimum distance a building must sit from a property line.

**Nonconforming use**: An existing use or building that was legal when built but does not meet current zoning.

**ADU (accessory dwelling unit)**: A second, smaller home on a single-family lot, such as a backyard cottage or garage apartment.

**Building permit**: Approval from the building department to construct, alter or repair a structure; it is inspected and then finaled.

**Finaled permit**: A permit whose work passed final inspection.

**Building footprint**: The outline of a building on the ground, usually derived from aerial imagery.

**MVT (Mapbox Vector Tile)**: A compact binary format for map data cut into tiles, used by Mapbox GL JS and MapLibre.

**MCP (Model Context Protocol)**: An open standard that lets AI assistants call external tools and data sources, such as the Parceled MCP server.