There is/There areis a common phrase in English, it is used to indicate that something "exists" or is in a certain location.
The main subject follows the verb when there is/are is used:
There is an apple on the desk. There are two cats on the car.
There is is used for singular or non countable nouns.
There are is used for plural nouns.
Since the main verb is the verb to be when we have to use a negative sentence we just add NOT to the verb:
There isn't a lamp behind the sofa.
There aren't any chairs in the room.
when the sentence is aquestion we just swap places:
Is there a restaurant near here?
Are there any parks?