The demonstrative pronouns

The demonstrative pronouns are this, that, these, and those. Like all pronouns, they replace nouns. Demonstrative pronouns are used to replace specific people or things that have been previously mentioned (or are understood from context).

A demonstrative pronoun tells us whether it is replacing something singular or plural and whether that thing(s) is close by or farther away.

This and That Represent Singular Nouns

This and that replace singular nouns.

This represents something close by. For example:

·         This is very smelly.

That represents something farther away. For example:

·         You can smell that from here.

These and Those Represent Plural Nouns

These and those replace plural nouns.

These represents something close by. For example:

·         These smell rotten.

Those represents something farther away. For example:

·         Do not paint those.

The Difference between Demonstrative Pronouns and Demonstrative Adjectives

The demonstrative adjectives are this, that, these, and those (i.e., the same words as the demonstrative pronouns). However, demonstrative adjectives modify nouns or pronouns. They cannot stand alone to play the role of a noun. For example:

·         This soup is very smelly.

·         You smell that factory from here.

·         These apples smell rotten.

·         Do not paint those fences.

http://www.grammar-monster.com/glossary/demonstrative_pronoun.htm