Demonstrative pronouns point to specific nouns or noun phrases that have already been mentioned (the antecedents) and they emphasize their importance by highlighting them.
Here are some examples:
* This book is my favorite. ("This" refers to a specific book previously mentioned)
* That house is beautiful. ("That" refers to a specific house already discussed)
* These cookies are delicious. ("These" refers to a group of cookies previously mentioned)
* Those flowers are stunning. ("Those" refers to a group of flowers already discussed)
By using demonstrative pronouns, the speaker or writer emphasizes the particular antecedent being referred to, making it clear and distinct.