In Passé composé or conversational past, most verbs use avoir as their auxiliary.
However, a fixed number of verbs use être as their auxiliary verb instead.
They are almost all verbs to do with movement:
To learn about this, see Agreeing past participle with subject's gender and number with (+ être) verbs in Le Passé Composé
The verbs to do with coming and going use être
La maison être