Since pronouns stand for nouns, they enable us to talk about a person, place or thing without constantly repeating the name.
Nouns and pronouns are called substantives.
Nouns and pronouns are very similar in their use. The difference between them is merely that the noun designates a person, place or thing by naming it, and that the pronoun designates, but does not name. Hence it is convenient to have a general term (substantive) to include both these parts of speech.
The substantive to which a pronoun refers is called its antecedent.
Frank introduced the boys to his father. [Frank is the antecedent of the pronoun his.]
Eleanor is visiting her aunt.
The book has lost its cover.
The trappers sat round their camp fire.
Washington and Franklin served their country in different ways. [Their has two antecedents, connected by and.]