A governor (ʿāmil) determines a word’s syntactic case; its governed word (maʿmūl) receives that relationship.
In ضَرَبَ زَيْدٌ عَمْرًا, the verb governs nominative «زَيْدٌ» as subject and accusative «عَمْرًا» as object.
An overt noun is explicitly expressed, like «زَيْدٌ», unlike a pronoun such as «هُوَ».