This term is used to describe pronouns . A pronoun always has a referent (i.e. a noun to which it refers).

The referent of 'I' is always the writer or speaker of a sentence and is referred to as the first person singular pronoun
'we' is called the first person plural pronoun
the person or people spoken to is referred to as the second person pronoun, i.e. 'you' (both singular and plural)
the person or people spoken about is referred to as the third person pronoun, i.e. he / she / it (third person singular) or they (third person plural).