How is a demonstrative adjective different from a demonstrative pronoun?

The demonstrative pronouns take the place of a nounindicating near or far in place or time.

The demonstrative pronouns are this, that, these, and those.

When placed just before a noun to describe the noun, the pronouns become adjectives.

Examples:

pronoun: These are mother's favorite flowers.

adjective: These flowers are mother's favorite.

pronoun: That was such fun.

adjective: That trip was such fun.