'His' and 'him' are both third-person pronouns. It means they are used to refer to a male person already mentioned or easily recognizable.
The difference between 'Him' and 'his' is in the uses of each pronoun in a sentence. 'His' is the possessive (also called the genitive) form of the pronoun 'he.'
'Him' is the objective (also called the accusative) form of the pronoun 'he.'
As you will see here, these two words carry different tasks in a sentence.
'Him' is an object pronoun which means it is used as an object in a sentence. More specifically, 'him' is the third-person singular object pronoun. Look at the following examples:
I love how the smallest things make
Here, 'him' is the direct object of the sentence.
You cannot share that secret with
Here, 'him' is the object of preposition.
Here, 'him' is the predicative that comes after the verb 'be'.
'His' is the possessive pronoun or the possessive determiner of the subject pronoun 'he'. 'His' shows someone's possession or ownership of something.
If it is followed by another noun, it is a determiner. On the other hand, if it appears without another noun, it is a pronoun.
'His' is followed by the noun 'dog' and shows that the dog is possessed by a male person.
My car was red.
'His' is a pronoun replacing the possessive phrase 'his car'.