There are two types of personal pronouns: subject and object.
1) Subject Pronouns - I, You, He, She, It, They, We Subject pronouns replace the name of the subject in the sentence. Example: Mrs. Yen did not come to school yesterday. She had to go to the doctor. "Mrs. Yen" is the subject and "she" is the subject pronoun.
2) Object Pronouns - Me, You, Him, Her, It, Us, Them Object pronouns take the place of the object in the sentence (the noun that receives the action in a sentence). Example: After Colleen bought a bike, it got stolen within a week, "it" is the object pronoun used to replace "bike."
More About Personal Pronouns
As mentioned above, personal pronouns help us to avoid constantly repeating the same noun over and over. The noun that is replaced is called theantecedent. Paying close attention to the antecedent will help you choose the correct personal pronoun.
Example: President Obama delivered a speech on health care reform. He spoke for more than an hour. "President Obama" is the antecedent to the personal pronoun "he."
To avoid confusion in sentences, it is important to choose the right personal pronoun that agrees in number (singular or plural), person (first, second, or third person), gender (masculine, feminine, neuter), and case (subject, object, possessive).