If even for a single moment you are not doing anything and you simply are, that’s what meditation is

Existence is that which happens, that which goes on happening.
Existence means that which goes on happening eternally. So anything that happens is Existence. You and everyone are happenings. This eternal happening is Existence.
There is no creator and no creation. Your birth is a happening, and your death will be a happening. Your being here is a happening. Your not being here will be a happening.