The words this, that, these and those are determiners. They are used to tell which thing or person you mean. These words are called demonstrative determiners or demonstrative adjectives.
I am keeping these books.
I am selling those books.
James lives in this house.
This ice cream is delicious.
How much is that racket?
What is that animal?
Bring me that ball.
Would you like these apples?
You use this and these to point to people or things near you.
You use that and those to point to people or things that are farther from you.
You use this and that before singular nouns.
You use these and those before plural nouns.