Definitions for "Participial phrase"
begins with a past or present participle and is followed by its object and modifiers; participial phrases are used as adjectives.
A phrase containing a participle and any modifiers. See for more information: 11 Rules of Writing Rule 8
a group of related words containing a participle ("ing" or "ed" forms of verbs) Again, "nonrestrictive" means nonessential, hence the need for comma(s)