An object is a noun which receives the action of a verb or verbal. It is in accusative case. When it is the object of a verb, it is often called a “direct object;” cf indirect object. An object is found by asking “what?”
Jeb built a house.
Ask yourself…”Jeb built what?” Jeb built a house. Hence, “house” is the object of the verb “built”.
An object is in the accusative case.