A "draft" is saved content for an email invitation. When you fill in a block of content (e.g., introduction, promo description, watermarking disclaimer, or footer), you have the option of saving that content as a named draft.

Why would I save an email invitation draft?

If you plan to re-send an invitation and don't want to copy/paste or re-type content into the invitation, you should save a draft. The next time around, select your saved draft, and the content automatically populates in the form.