It is often used at the beginning of a sentence to introduce a question, statement, or command, similar to "So, you..." in English.
Here are some examples:
* Alors tu veux manger un gâteau? (So you want to eat a cake?)
* Alors tu es d'accord? (Well, you agree?)
* Alors tu dois aller au lit. (So you have to go to bed.)
The phrase can also be used in a more informal way to express surprise, amusement, or disbelief.
* Alors tu as fait ça? (So you did that?)
* Alors tu es parti sans moi? (So you left without me?)
* Alors tu as gagné au loto? (So you won the lottery?)
It is important to note that the intonation and context will often determine the precise meaning of "Alors tu."