In English no matter to who you are speaking to, you’ll always use ‘you’ but in French it’s not the same.
je, tu, il/elle, nous, vous, ils/elles // I, you, he/she, we, you, they
If you are talking to a friend, someone younger than you or a relative, you will use ‘tu’. But if you are talking to someone older than you, old people, a teacher, your boss, someone you have never met, you will use ‘vous’, even if you are talking to one person, it’s a sign of respect. Of course, the verb will be conjugated according to ‘vous’ or ‘tu’.
- Madame, vous prenez l’ascenseur ? (Miss, do you take the elevator ?)
- Tom, tu prends l’ascensseur ? (Tom, do you take the elevator ?)
In both cases, we are talking to one person, but in the first example, we’ve never met the person so we use the pronoun ‘vous’ with the verbal ending in ‘ez’, and in the second example, Tom can be a friend so we use the pronoun ‘tu’ and the verbal ending of the verb ‘prendre’ in ‘ds’.
When you use ‘tu’ to speak to someone, we say: ‘tutoyer quelqu’un’ (to call someone ‘tu’), and if you use ‘vous’ to speak to someone, we say: ‘vouvoyer quelqu’un’ (to call someone ‘vous’).