A direct object receives action from the verb.
To put that another way, the direct object gets acted upon.
Look at these sentences. The direct object in each sentence is the dark bolded word.
Notice that each dark bolded word is a noun.
Jackie threw the ball.
Peter dropped his book.
My brother and I watched a movie.
You can find the direct object by reading the first part of the sentence and then asking what?
Jackie threw what?
Peter dropped what?
My brother and I watched what?
The answer to each question is the direct object. The direct object is always a noun.
These sentences are missing a direct object. Can you fill in each blank with a noun?
Jim ate a __________.
Billy showed me his new __________.
Here are some possible nouns for the first sentence: hot dog, cookie, peanut, hamburger, doughnut
Here are some possible nouns for the second sentence: Lego set, phone, shoes, game, train, football
The direct object in a sentence is always a noun.