A demonstrative pronoun represents something or someone and performs as a noun.
e.g. We are chatting about this and that.
This is Kookie speaking.
That is a good idea.
A demonstrative adjective performs as an adjective.
e.g. Those worms were big yesterday, weren't they?
The following words may be demonstrative pronouns or demonstrative adjectives.
They depend on the context of the sentence.
near in distance or time - this + these
far in distance or time - that + those