What is the difference between Tu and Vous? (and when should one be used over the other?)

Tu and vous are subject/personal pronouns that affect the way you conjugate a verb (just like Je, Il, Nous, etc.). While tu is a singular pronoun, vous is both a singular and plural (as you can be addressing "you" or "they")The confusion with tu and vous, tends to be that they both translate to "you". The difference is that tu is only used when you are talking about one person, and is used in a personal context amongst friends and family. Vous can be used when talking about one person: and is used in a more formal/polite context, or is used when talking about a group: "they".