It literally translates to "There are of rooms," but the "of" is understood in English.
Here are some examples of how to use it in a sentence:
* "Il y a de chambres dans l'hôtel." (There are rooms in the hotel.)
* "Il y a de chambres disponibles." (There are rooms available.)
* "Il n'y a pas de chambres libres." (There are no rooms free.)