We can use relative clauses to join two English sentences together, often to give more information about something.
I bought a new car. It is very fast.
→ I bought a new car that is very fast.
We use relative pronouns to add these sentences together. They are:
who / which / that / whom (to who) / whose (possessive) / when / where
There are 2 types of relative clauses: the defining relative clause and the non-defining relative clause