Subject pronouns identify who performs the action of a verb. Je means "I," and like several French words it elides before a vowel or mute h, becoming j', as in j'aime ("I love"). Tu means "you" in the singular informal sense, used with friends, family, children, and peers. Vous has two roles: it is the plural "you" for addressing groups, and also the formal singular "you" used with strangers, elders, and professional contacts. Choosing between tu and vous is one of the first social decisions a French learner makes.
For third-person pronouns, gender matters. Il means "he" or "it" for masculine nouns, while elle means "she" or "it" for feminine nouns, as in Elle est belle ("She is beautiful"). Il also serves as an impersonal pronoun in expressions about weather: il pleut means "it's raining." Nous is "we," although in everyday spoken French you will frequently hear on instead, even in grammatical contexts where nous would be more formal or correct.
Plural third-person pronouns obey a strict rule in French. Elles means "they" only when the entire group being referred to is female. If even a single male is present in the group, French switches to the masculine ils. This rule applies regardless of how many women are in the group — one man among many women is still ils. The same masculine-wins principle is foundational for keeping track of grammatical gender in many other situations across the language.