Avere or essere in compound tenses?

Grammatica centrale

When do you use avere and when do you use èssere in compound tenses?

Avere and essere serve as auxiliary verbs (verbi ausiliari) in compound tenses. Auxiliary verbs in Italian come before the past participle (participio passato).

Grammatically speaking, the auxiliary verb indicates the tense, mood, and so forth while the past participle provides the mean…