A Relative Pronoun refers to the noun or pronoun before it . It is also used to join two sentences together.

e.g.

1. The boy who is playing is my brother.

2. I asked him whose car that was.

3. The man whom you met was my uncle.

4. The books which you bought were cheap.

5. The film that everyone enjoys is very good.

Note :

Who or Whom is used for people.

Which or that is used for animals and things.

Whose is used for people and animals.