It's usually the general provisions and structuring for land use in a city. You can usually go to the particular city (since you didn't mention the house address or city) and see what their provisions are (how that piece of land coordinates with their land use).
Hope this helps. If you have any other questions, please feel free to contact me.
Your local or county zoning/planning office maintains a set of rules and regulations for how one may use a parcel of land. Typically, those uses are divided into commercial and residential classifications; there are also several subcatagories within each classification.
The point is that you'll need to contact your local/county zoning and planning dept for more details.