When working with British records, the counties as appearing in Pedigree Forge are the Historic Counties.[1] The use of these has gradually eroded over the years, as modern Council Authorities have been confused the matter. The problem being that these modern council areas are forever changing, whereas the historic counties are as they have always been. It is recommended that you consider using the Historic Counties, when recording places in the British Isles.
This does cause some confusion however, particularly in regard to London, which has absorbed a lot of the surrounding places, originally in a different county. For example, Southwark is in the historic county of Surrey, and much of the area of “London” north of the Thames is in the historic county of Middlesex.
Some counties are, or have, been known by more than one name, or by variations in spelling. Either are accepted and recognised by Pedigree Forge, but the way that they are output in reports, and charts, or suggested from the list of places, can be configured using “Tools” then “Options” from the main menu bar:
Suggestions for Region in Other Countries:
[1] The Historic Counties Standard, The Historic Counties Trust https://historiccountiestrust.co.uk/standard