Here is a list of all documented concepts with brief descriptions:

[detail level 123]

▼Ncppgres
▼Nutils
Ris_optional
Rstd_tuple
Rconvertible_into_datum
Rconvertible_from_datum
Rconvertible_from_nullable_datum
Rconvertible_into_nullable_datum
Rerror_formattable
Rdatumable_tuple
Rconvertible_into_nullable_datum_and_has_a_type
Rconvertible_into_nullable_datum_or_set_iterator_or_void
Rdatumable_function	Function that operates on values of Postgres types
Ra_memory_context
Rnode_tagged
Rnode_xpr_tagged
Rnode_inherited_base
Rnode_inherited
Rnode
Rdatumable_iterator
Rsyscached
Rflattenable
Rexpanded_varlena_type
Rhas_a_type