In passé composé, you need to choose an auxiliary verb, either aller or être.
French teachers usually simplify the rule and say: If a verb is on the DMV list, use être.
J'ai parlé → Not DMV. Use avoir.
Je suis sorti → DMV. Use être.
The full rule throws a small wrench in the gears. A DMV verb only uses être if it has no direct object. (Also, any verb can ...
I'll give you an example, in French, you'd say:
Il est allé marcher (he went for a walk)
Il a allé marcher
Because 'Aller' belongs to the 'Vandertrampp list'. In other words, you'd use the 'être' auxiliary verb, not the 'avoir'.
To be honest I had never heard about that list, and I wouldn't apply it to the letter.
For instance, the first M is ...