You use these when you refer to something which you expect the person you are talking to to know about, or when you are checking that you are both thinking of the same person or thing.
Definition of these in Oxford Advanced American Dictionary. Meaning, pronunciation, picture, example sentences, grammar, usage notes, synonyms and more.
This and these are demonstratives, which means they indicate a specific noun in a sentence. The two words are similar because they refer to nouns that are near in space and time.