Now I'm starting to become confused.
It seems that the meaning of Closed" wrt airfields in the UK might be also a bit like calling "Ready" at the holding point. On more than one occasion I've heard foreign crews mainly with English accents calling "Fully Ready". WTF? Either you're ready or you're not.
To me an airfield's either closed or it's not. How can it be closed when some people are still using it? Should there be a "Fully Closed" option as well?
I like the way we do it over here.
There's public and private. Prior permission is required to land at a private airfield whereas it's not required at a public field. Both types can be licensed or unlicensed, or for that matter controlled or uncontrolled,
There's licensed or unlicensed. Licensed means the T/O and landing distances and the approach/departure fans etc have been surveyed by appropriately qualified people. Licensed fields are in the AIP whereas unlicensed are generally not in the AIP. ATO ops generally require a licensed field, the main exception being part 135 ops. Licensed does not infer provision of ATC or RFS.
There's controlled and uncontrolled. When a tower goes off watch the airport stays open but becomes uncontrolled. ATO's can be carried out with or without ATC though once traffic levels and or seat capacity thresholds are exceeded ATC must be in attendance.
RFS services are only required for RPT services and in some instances are only available for arrivals and departures.
When an airport is closed, it is closed, no ifs, buts, or maybes. The closure may be permanent, or may be temporary, due to surface conditions, (flooding etc), or seasonal e.g. haymaking, lambing season etc.