An object in a sentence is always a noun. An object in a sentence does nothing. The action happens to the object.
With a direct object, the action happens directly to the object. The direct object directly receives the action.
Bob drives the truck.
The noun truck is a direct object. The truck directly receives the driving action. The subject Bob transfers the driving action to the truck.
Here are more examples of a direct object:
Mom baked a cake. The noun cake receives the action.
Sarah studied her history lesson. The noun lesson receives the action.
The bird sang a song. The noun song receives the action.
A direct object receives the action in a sentence. A direct object is always a noun.
▶It’s your turn. Find the direct object in this sentence. A stone hit our window. Did you find that noun that received the action? Good for you!