Learn French: Elles se maquillent devant un miroir. - They are putting on makeup in front of a mirror.

The verb maquiller means "to put makeup on someone else." By adding the reflexive pronoun se, it becomes se maquiller, meaning "to put makeup on oneself." Since the subject is Elles (They), the matching reflexive pronoun for "themselves" is se.

Do I pronounce the "-ent" at the end of maquillent?

No. For regular "-er" verbs like se maquiller, the -ent ending used for ils and elles is completely silent. You pronounce maquillent exactly like the singular form, maquille.

In English, "makeup" is a noun. Is it just one verb in French?

Yes! While English uses a verb phrase ("putting on makeup"), French uses a single reflexive verb: se maquiller. You don't need a separate word for "putting on" or "makeup" here because the verb covers the whole action.

I thought "before" was avant. Why use devant here?

Both can translate to "before" in English, but they have different uses. Devant is about physical location, meaning "in front of" (like a mirror or a building). Avant is about time, meaning "before" an event happens.