Participial Phrases

It's a phrase that begins with a present participle (ending in-ing) or past participle (ending in -en or -ed). A participle is a type of verbal, it is a word formed from a verb that is used as an adjective to modify nouns, but functions as another part of speech. A participial phrase is made up of the participle, its modifiers, and other words needed to complete the idea begun by the participle. It commonly functions as an adjective.  

A participial phrase can be formed from relative clause, adverbial clause or a simple sentence. Besides, it can be in continuos form (being shown) or perfect form (having been shown).  

Like clauses, participial phrases can be restrictive or nonrestrictive. If the original clause is restrictive, the participial phrase formed from it will be also restrictive. Participial phrases are punctuated the same way as clauses; that is, it depends on whether the participial phrase is restrictive or nonrestrictive. A restrictive phrase is not punctuated with commas since it is necessary to correctly identify the noun phrase it modifies. However, a nonrestrictive phrase is punctuated by commas since it gives additional information about the noun it modifies. 

Working hard all year, the student finished his thesis by fall semester.  
   - Working is the participle (functioning as an adjective, describing the student).  

Stolen by the hackers, the passwords were changed at once.    
  - Stolen is the participle (functioning as an adjective) describing the passwords.

Actors which have competed in the Grammy awards can early attend the ceremony.      
  - (Perfect / restrictive participial phrase) 

The books, that were being distributed in class, support students with learning difficulties.  
  - (Continuos / nonrestrictive participial phrase)