Grammar: Groups & phrases: Verb group: Structure of the verb group

Voice: active and passive

Structure of the verb group in passive voice clauses

The auxiliary be is used to express the 'passive voice' in the verb group:

The ghost   was     chased  around the flat by the children. [passive voice]                  aux verb   main verb                            verb   group

The verb group in a passive voice clause is made up of the auxiliary be plus the -ed /en form of the main verb, traditionally called 'past participle'. The exact form of the auxiliary be depends on person, number and tense (am, are, is, was, were), and the exact form of the -ed /en form of the main verb depends on the main verb itself:

The dog was hit. (to hit: no change to verb) 
The newspapers were taken. (to take: -en ending)
The door is being opened. (to open: -ed ending)

The function of the be auxiliary, called 'Finite', anchors the verb group in the present time and place. It expresses information about the Subject (person, number) and the time of the process (tense, aspect). By contrast, the function of the main verb, called 'Event', expresses what is happening.

Mrs Gong  was  taken  on a tour of the school by Miss Lee.                 Finite   Event

Note that the terms Finite and Event are written with an initial capital to remind us that they are functional terms.