Pronoun is the word which is used at the place of noun. While addressing someone or oneself, it sounds very odd to use the name every time. So, to avoid this we use pronoun.
While talking about ourselves, we never use our name because it is already understood. So we always use the pronoun ‘I’. For example.
I have done this.
I am a doctor.
You are an engineer.
He helped me a lot.
We are from Mumbai.
This form of pronoun(I, You, We, He, She, It) is called Nominative.
Let’s take one more example to understand another type of pronoun.
This is my car.
Here the word ‘my’ is talking about the ownership or possession. So it is called the possessive case of the personal pronoun. This case of the pronoun also does the work of an adjective. That’s why they are called pronominal adjectives.
The above statement can also be written as
This car is mine.
Here ‘mine’ is the possessive case of the personal pronoun. Therefore, the possessive case always has two forms.
He taught me English.
Here ‘me’ is the personal pronoun. This form of pronoun is called Accusative Case.
In brief, personal pronoun are of three types.
1. Nominative
2. Possessive
3. Accusative
For second person
1. Nominative- You
2. Possessive- Your and Yours
3. Accusative- You

For Third person

1. Nominative- He, She, It, They
2. Possessive- His, Her, Hers, its, their, theirs, our, ours
3. Accusative- Him, Her, Them, Us