This is a common greeting used in China, especially among friends, family, and colleagues. It is a polite way of asking if someone has had their meal.
Here's a breakdown of the characters:
* 你 (nǐ) - you
* 吃 (chī) - to eat
* 饭 (fàn) - rice (often used as a general term for food)
* 了 (le) - a particle indicating completion of an action
* 吗 (ma) - a question particle
So, the entire phrase means "You ate (rice/food) already, didn't you?" or "Have you eaten?"