Questions & Answers about Je vous le rendrai après-demain si je suis occupé.
Why is it Je vous le and not Je le vous?
French object pronouns have a fixed order before a conjugated verb: me/te/se/nous/vous + le/la/les + lui/leur + y + en. Here, vous (to you) must come before le (it). So Je vous le rendrai is correct; Je le vous rendrai is wrong in a normal statement. Exception: in the affirmative imperative the order flips and hyphens are used, e.g., Rendez-le-moi, Rends-le-moi.
What exactly does vous mean here—formal singular or plural?
What does le stand for? What if the thing is feminine or plural?
Le replaces a previously mentioned masculine singular direct object. For a feminine object, use la: Je vous la rendrai. For a plural object, use les: Je vous les rendrai. If you refer to an amount or something introduced by de, use en: Je vous en rendrai quelques-uns. With rendre, the person is indirect (à quelqu’un) and the thing is direct, hence vous (COI) + le/la/les (COD).