A pronoun is a word used to refer to a noun mentioned earlier in the text. This noun is called the antecedent of the pronoun.
Susmita is a pretty girl. She also sings well. (Pronoun – she; antecedent – Susmita)
Note that the pronoun must agree with its antecedent in number and person. That means if the antecedent is a singular noun, then the pronoun used to refer to it, too, should be singular in number. >>>