A predicateconsists of a verb or verb phrase and its complements, if any. A verb that requires no complements is called intransitive.
A verb that requires one or two complements is called transitive.
A verb may belong to both categories.
We may generate the complete sentence "I walk." with no complements. We may also generate "I walk home.", where "home" is a complement of the verb. Further, "I walk my dog home." has two complements: "my dog" and "home". In traditional grammars, these complements are called the "indirect object" (my dog) and the "direct object" (home).
The complement of a verb or verb phrase is described as being optional and consisting not only of objects, but of adjectives, prepositional phrases, etc.