Ye Gods I sometimes despair of the human race
a closed airfield is like a closed retail store, garage, theatre. It means that it is not accessible without specific negotiation with the owner.
An unlicensed airfield is just an airfield which can't be used by any operator that requires a licensed airfield. Private flights and training flights in a light aircraft are highly unlikely to need a licensed airfield since the requirement for training to take place from licensed airfields was removed in 2010. Even before then flights with instructors could include unlicensed and even foreign airfields!