(1) The agent is unmentioned. (2) The original object is promoted. (3) The promoted element is nāʾib al-fāʿil and is nominative. (4) The verb is passive. (5) Singular/dual/plural and gender agreement parallel the rules learned for subjects.
The book’s core example is ضُرِبَ زَيْدٌ. The next source section begins mubtadaʾ and khabar, which belongs to the next lesson.