In Le Passé Composé, most verbs use avoir as the auxiliary verb but a fixed number of verbs use être instead.
They are almost all verbs to do with movement (See Conjugate coming and going verbs (+ être) in the compound past in French (Le Passé Composé)), but also those to do with states of being (birth, death, becoming, staying).
Learn how to conjugate NAÎTRE (to be born),RESTER (to stay/to remain), MOURIR (to die) and DEVENIR (to become) in Le Passé Composé (Indicatif) in French
The pattern for these verbs in Le Passé Composé:
être (le Présent) + past participle of the verb
Because they're using être as auxiliary verb, their past participles have to agree with the subject of the verb.
List of the "being and state" verbs and their past participles
Want to make sure your French sounds confident? We’ll map your knowledge and give you free lessons to focus on your gaps and mistakes. Start your Braimap today »