French phrase
Pourquoi tu as fait ça ?
Meaning
Why did you do that?
When to use it
This asks why someone did something. It is casual and common among friends.
Example dialogue
Tu as pris mon ballon !
You took my ball!
Pourquoi tu as fait ça ? Je pensais te le rendre plus tard.
Why did you do that? I thought I'd give it back to you later.