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.
and when the sentence is a question we just swap places
Is there a restaurant near here?
Are there any parks?
Time to practise!!!