Per the Library Finder technical approach document, we need a way to distinguish between catalogs with different types of service areas. We know of these types:

• local - serving the people in a small geographic area such as a city.
• county - serving the people in an administrative subdivision of a nation. In the US these are called "counties", I don't know about other countries.
• state - serving the people in an administrative division of a nation; this may be called a "state", "province", "prefecture", etc. depending on the country.
• national - serving the people of a nation.
• universal - serving everyone, everywhere.

This is related to the audiences extension, but that extension was designed to talk about the patrons of libraries, and this is for talking about their service areas.

Currently we can specify a library's service area very precisely, as a GeoJSON polygon, but that's too much information; we need to summarize it with a single piece of information.

"county", "state", etc. are members of a controlled vocabulary and not the literal strings that will be presented to users; they can be localized.