Learn French: Vous devez écrire le rapport. - You have to write the report.

Devez is the matching form of the verb devoir (must / to have to) when used with vous. It is an irregular verb, so its present tense forms are: je dois, tu dois, il/elle doit, nous devons, vous devez, and ils/elles doivent.

Could this also translate to "You must write the report"?

Yes! English has a slight difference between "must" and "have to", but French uses devoir for both. Vous devez can be translated as either "You must" or "You have to" depending on what sounds best in English.

Why isn't the verb écrire conjugated here?

In French, when two verbs are used together to express a single idea, only the first verb is conjugated. The second verb stays in its infinitive (unconjugated or dictionary) form. That is why the conjugated devez is followed immediately by the infinitive écrire (to write).

How do I know to use le before rapport?

Rapport is a masculine noun, so it requires the masculine singular article le (the). Because there isn't a strict rule to guess a word's gender just by looking at it, it is always best to memorize the article alongside the noun when learning new vocabulary!