The past participle used to form the passive voice

The past participle is used to form the passive voice (be + past participle) as well as the passive forms of infinitives, gerunds and the present and perfect participles. When used in this way, it is sometimes called the passive participle:

Penicillin was discovered by Alexander Fleming in 1928. (past simple passive)
I have the feeling I've been misunderstood. (present perfect passive)
Josh always needs to be told what to do. (passive simple infinitive)
I hate being lied to. (passive simple gerund)
Authorities refused to reveal any information about the case being investigated. (passive present participle)
Having been nominated three times for an Oscar, he is one of today's most acclaimed film directors. (passive perfect participle)

The past participle can in itself have a passive meaning:

There was a handwritten note on the table.
Damaged badly by the flood, the school had to be rebuilt.