Why do some verbs use avoir and some être in the past tense?

This rule might seem tricky at first. However, it is actually quite easy to follow after a bit of practice. Generally speaking, avoir is the main verb used to form the past tense. This is really similar to english.  For example: French: Il a mangé une banane. English: He has eaten a banana Sometimes, however, you will see the verb être used in some cases. In order to know whether to use avoir or être, you have to look at the main verb you are using. In the case above, the main verb was manger (to eat) and it took the avoir form. But some verbs are a bit more 'special' that that and, therefore, they take the être form. These are the following: a) verbs that express 'movement', such as arriver (to arrive) and sortir (to leave) - please see below for all other verbs that use être. b) reflexive verbs Movement verbs can be memorised through the following Mnemonic:Try and remember the phrase DR & MRS VANDERTRAMP'. Then, look at what verb each letter represents.Devenir Revenir & Monter Rester Sortir Venir Aller Naître Descendre Entrer Rentrer Tomber Retourner Arriver Mourir Partir Voila! Don't worry if this seems a little bit complicated . Just read through it again and ask me if you have any other questions on it! :)