The personal pronoun is also known as the subject pronoun. The subject personal pronouns are classified into two categories: Persons singular and Persons plural.
1. Structure
All verb conjugations in French have six “persons.” Three are singular, corresponding to: I, you (familiar), and he/she/it/one. Three are plural, corresponding to: we, you (pol. singular, and fam. or pol. plural), and they. 

Usage

Conjugated verb forms in French are always preceded by a noun or a subject pronoun. 
To avoid repetition, the subject pronoun often replaces a noun. 

Richard est en ville. Il est au cinéma. (Richard is downtown. He is at the movies.)
Mes sœurs sont en voyage. Elles sont à Lille. (My sisters are on a trip. They’re in Lille.)
Je (I). In French, je is capitalized only when it begins a sentence. Like the definite articles le and la, je drops (elides) the letter -e before a vowel sound. It is replaced by an apostrophe and closed up to the conjugated verb. 
Je suis content; j’ai un I am happy; I have a new job. nouveau travail. 
Tu and vous (you). Tu (with its verb form) is always singular. It is used to speak to one person who is a friend or relative, to a child, or to a pet. Vous is used to speak to someone you don’t know well or to anyone with whom you have a relationship of respect, for example, strangers, new acquaintances, salespeople, or professionals. The plural of both tu and vous is vous (with its conjugated verb form). 
Sylvie, tu es étudiante? (Sylvie, are you a student?)
Pardon, Madame, vous êtes la mère de Sylvie? (Excuse me, Ma’am, are you Sylvie’s mother?)
Attention les enfants! Vous êtes prêts? (Children! Are you ready?)

Il and ils; elle and elles. The English subject pronouns he, she, it (singu- lar), and they (plural) are expressed by il or ils (for masculine nouns) and elle or elles (for feminine nouns). 
Elles sont formidables! (They (fem. persons or things) are fantastic!)
Il est drôle. (He/It (The puppy[?]) is funny. )
The plural ils (they, m. pl.) refers to any group that includes at least one masculine noun.

Voilà Marie, Anne et Patrick. There’s Marie, Anne, and Patrick. 
- Ils sont en retard! (-They’re late!)

On. The subject pronoun on (third-person singular) is used in French to convey the English indefinite subjects one, we, people, and they. 
Alors, on est d’accord? (O.K., so we agree?)
Le matin, on est en bonne forme. (In the morning, they (we, people) feed good)

Modern speech often replaces nous (we) by on. The adjective can be spelled in the singular or the plural. 
Vous êtes fatigués? (You’re tired?)
- Oui, on est très fatigué(s)! (- Yes, we’re all (everybody’s) very tired!)
- Oui, nous sommes très fatigué[e]s!) (- Yes, we’re all (everybody’s) very tired!)

2. Exercise

Exercise 1: Complete with a personal pronoun

1. Marie et Michel _________ sont mariés.
2. Sophie et Jeanne _________ amies depuis longtemps.
3. Ma femme et moi _________ aimons le ski.
4. Toi et Amélie _________ allez en vacances à Rome.
5. Elle et moi _________ vivons dans la même rue.
6. Au Brésil, _________ parle portugais.
7. Nos amis, _________ ne viennent pas ce soir à la maison.
8. La boulangère _________ est très sympathique.
9. Moi et mes parents _________ habitons cette petite maison.
10. Cet exercice de grammaire _________ est maintenant terminé.

Key: 
1. ils 
2. elles
3. nous/on
4. vous
5. nous/on
6. on
7. ils
8. elle
9. nous/on
10. il