Questions about Pronominal Verbs
Q: Why is it je me couche and NOT je couche?
Some French verbs are always used with a preceding pronoun.
Q: Why is it je me suis promené and NOT je m'ai promené?
All pronominal verbs use être in the passé composé and plus-que-parfait tenses.
Q: Why is it il s'est lavé les mains and NOT il a lavé ses mains?
With body parts, use the pronominal verb se laver. Note also that the determiner should be les rather than the possessive determiner ses.
Q: Why is it je vais me laver les mains and NOT je vais se laver les mains?
Even after helper verbs like aller, pouvoir, vouloir and devoir, the pronoun must correspond to the subject.
Q: Why is it Paul se concentre sur ses devoirs and NOT Paul concentre sur ses devoirs?
This is simply one of those verbs that has to be used with a pronoun before the verb.
Q: Why is it ils se sont parlé and NOT ils se sont parlés?
The verb parler is followed by an indirect object (on parle à quelqu'un). Since one does not show agreement with indirect objects, the past participle doesn't change (parlé).
Q: Why is it elles se sont vues and NOT elles se sont vu?
The verb voir is followed by a direct object (there is no preposition after it). Since past participles agree with preceding direct objects, you need to indicate feminine and plural agreement on the past participle.