Property class
A code the assessor gives every parcel based on its use, such as 1 for vacant land, 2 for residential, 3A or 3B for farms, 4A for commercial, 4B for industrial, 4C for apartments, and 15A to 15F for exempt property.
New Jersey example
A one to four family house is Class 2. An apartment building is Class 4C. On a farm that qualifies for farmland assessment, the land is Class 3B, while barns and silos are assessed under Class 3A. A public school is Class 15A. Railroad property uses 5A or 5B.
Official source
MOD IV User Manual (NJ Division of Taxation, Property Administration, 2024 updates)
This is a plain-English summary. Rules and dollar amounts change, so check the official source or a professional before you file or sign anything.