There has two meanings, one for location - (the book is over there), and another as a sort of general subject pronoun (there's nothing happening). If there is another pronoun (what) we don't use there in the sentence (Note, this sentence isn't asking about what is happening at a particular location)
I can say - What's happening? (Wat gebeurt er?) I don't use there in this sentence, although Dutch uses it. . The answer could be "There's nothing happening" (Er is niets gebeurt) The "there" in this sentence is a general subject pronoun, used like er in the Dutch sentence. I can say What's happening there, (location). ( Wat daar gebeurt.) with an answer of There's nothing happening there, (Er is niets daar gebeurt) which shows both uses, one for the pronoun (the first),. and one for the location (the second). Dutch has two different words translating as there. (Or English has two words that look and sound the same but mean different things) Note, these are all Google translations, which may or may not be accurate.