What does it mean word for word?
The component qu'est-ce que literally translates to 'what is it that' and serves as a standard way to introduce a question starting with 'what'.
Which one should you use?
The choice of phrase depends on who you are addressing and the level of formality. qu'est-ce que tu fais ? is the informal way to ask the question, while Qu'est-ce que vous faites ? and Que faites-vous ? are used when addressing multiple people or when using the formal 'vous'. For very casual speech, Tu fais quoi ? is used.
Is there a formal and an informal way to say it?
There are several ways to express this depending on the situation. qu'est-ce que tu fais ? is used in informal settings. For formal situations, you should use Qu'est-ce que vous faites ? or Que faites-vous ? In relaxed, casual spoken French, you might hear the colloquial Tu fais quoi ?
Is it said differently in some regions?
In countries like Canada, the colloquial expression Tu fiches quoi ? is used to mean 'What are you doing?'
How does it change in a sentence?
To address more than one person, or to use the formal 'vous' form, change the phrase to qu'est-ce que vous faites ?
Did you know?
Example conversation
Manon walks into the kitchen and sees Hugo cooking.
- ManonSalut Hugo, qu'est-ce que tu fais ?Hi Hugo, what are you doing?
- HugoJe prépare le dîner pour nous.I am preparing dinner for us.
- ManonC'est très gentil de ta part !That is very kind of you!
- HugoC'est presque prêt, attends un peu.It is almost ready, wait a bit.
Sources
- Word origins: Wiktionary entries que, tu, CC BY-SA 4.0.