What: the thing(s) that/which

"What" does not refer to a noun that comes before it. It acts as noun + relative pronoun together, and means 'the thing(s) which/that . (Michael Swan)

I. What she said made me angry.
II. This is exactly what I wanted.

1. What does " noun + relative pronoun together" in the above mean?
2. "What" means "the thing(s) which/that " . Could anybody explain the meaning of "the thing(s) which/that " to me, please? I find it difficult to explain to children?

Thanks.

Could anybody help, please?

She said something.
The thing (noun) that (relative pronoun) she said made me angry.
What (= the thing that) she said made me angry.

She did some things that made me angry.
The things that she did made me angry.
What she did (= the things that) made me angry.