Hopefully this explanation can help clear everything up!
Demonstrative pronouns describe where a noun is in location to the speaker. All pronouns replace the noun. Using the correct demonstrative pronoun depends on if the object is near or far, singular or plural.
This and that replace singular nouns.
This: replaces a singular noun that is near
“Would you like to try my food? This tastes really good!”
That: replaces a singular noun that is far
“What type of food are you eating? That looks delicious.”
These and those replace plural nouns.
These: replaces a plural noun that is near
“Come here and look at the flowers. These are beautiful!”
Those: replaces a plural noun that is far
“The flowers over there look prettier. Those are better.”
So take this information and apply it to speaking English!