[[An appositive relative clause is a clause that is formally identical to a relative clause but does not serve to restrict the reference of the nominal of which it is part.]]
Comments
Another widely used term is "nonrestrictive relative clause".
"Alongside of [relative clause]s, languages normally have a variety of structures that resemble [relative clause]s in various ways, without meeting the definition in (1). In English and many other languages, there is, for example, the so-called ‘nonrestrictive’ relative clause, which makes a comment about an NP or other constituent, without delimiting its reference." (Andrews 2007: 207)