Boş oda var mı

I assume you want a translation to English.

Is there a vacancy? (Do you have any vacancies?)

Boş oda = vacant/empty room

var mı? = is there/are there?

This is a question usually asked in hotels or pensions to find out whether they have any rooms left for accommodation.

The response can be

Boş oda var  or  Boş oda yok