Two purposes are served by a demonstrative pronoun in English: It indicates an object without identifying it and expresses the speaker’s proximity to the object.
There are four examples of demonstrative pronouns: this, that, those and these. ‘This’ and ‘these’ refer to objects that are close to the speaker, while ‘that’ and ‘those’ are used to indicate that the object referred to is far away.
There is often confusion between demonstrative pronouns and adjectives. ‘This,’ ‘that,’ ‘those’ and ‘these’ are not always used as pronouns; they can sometimes serve as demonstrative adjectives. Adjectives are words that describe nouns. You can tell if these four words are being used as pronouns or adjectives by observing whether or not the demonstrative word is followed by a noun.
“That car is fast,” for example. Here, ‘that’ is used as a demonstrative adjective because it is followed by the noun it indicates. The word ‘that’ in this example describes something about the car, namely, that it is “over there” as opposed to “right here.” On the other hand, a demonstrative pronoun is the subject of its sentences.
There is one gray area for this rule; demonstrative pronouns can be used in a sentence with the name of the person they refer to. “That is John,” for example. ‘That’ is still the subject of the sentence. ‘John’ gives information about what ‘that’ is. Other than this type of usage in sentences referring to people, demonstrative pronouns are used only to refer to things.