This is a glossary of terms used in this site.

Postcode Area

The postcode area is the largest geographical unit used by Royal Mail for the purposes of directing mail.
It forms the initial characters of the alphanumeric UK postcode.
There is currently a total of 121 geographic postcode areas in use in the United Kingdom, with a further 3 covering the Crown Dependencies of Guernsey, Jersey and the Isle of Man.
Postcode areas are subdivided into postcode districts.

Post Town

The post town is a basic unit of the United Kingdom mail delivery system.
Post towns rarely correspond to political boundaries. They usually correspond to one or more postal district, though in some cases several post towns make up one postal district.
Post towns are useful for distinguishing between multiple localities or streets that share the same name, but are situated in different areas.

Postcode District

A postcode district is a geographical unit used by Royal Mail.
It is a subdivision of a postcode area. It consists of the first part (before the space) of a UK postcode.
One or more postcode districts usually make up a post town, however on rare occasions, more than one post town may make up a single postal district.