There are 16 verbs in French that require être rather than avoir in the passé compose. Sometimes there is a passé. Passé uses être to talk about physically passing by something. These irregular verbs also must agree in gender and in number.
I am a grammar nerd. It goes against everything I do as a teacher, but I love it and it's how I learned French. Now I teach using TPRS with whole language chunks and rarely do any explicit grammar teaching