It's a common question used to inquire about someone's activities, especially over a period of time.
Here's a breakdown of the phrase:
* Que: This is the interrogative pronoun "what".
* has: This is the present perfect tense of the verb "haber", meaning "have".
* estado: This is the past participle of the verb "estar", meaning "being".
* haciendo: This is the gerund of the verb "hacer", meaning "doing".
So, the phrase "Que has estado haciendo" is asking, "What have you been doing (while being in a particular state or situation)?"