Is relative and indefinite category of pronouns?

Answer 1

Yes, they are:

A relative pronounpronoun is a word that introduce a relative clause, it "relates" to the word that it modifies.

They are: who, whom, whose, which, that.

An indefinite pronoun is a word that takes the place of a noun (or noun phrase) that is an unknown or unnamed person, thing, or amount.

They are: all, another, any, anybody, anyone, anything, both, each, either, enough, everybody, everyone, everything, few, fewer, less, little, many, more, most, much, neither, nobody, no one, nothing, none, one, other, others, several, some, somebody, someone, something, such, and they (people in general).

Example sentences:

The man, whose car was hit, was very angry.

Everyone has left the building but many are still waiting for their ride.

Answer 2

Relative pronouns (e.g. who, which, that) are used to introduce relative clauses that provide more information about a noun in a sentence. Indefinite pronouns (e.g. someone, anything) refer to non-specific people or things without specifying exactly who or what is being referred to.