Jefe is right of course, as we do not know exactly. We do have some ideas however. Our Universe as we now understand it is thought to have originated with the Big Bang event, about 14 billion years ago.
The Cosmos could be a different thing, and it could have existed prior to the big bang. Obviously something did, as the elements that caused the BB were already present.
rays, the Big Bang was not an instantaneous explosion. It was an expansion. It was actually the evolution of our universe into it’s present state, not necessarily the beginning of the Cosmos. The Cosmos could have existed for billions of years or even infintely before the Big Bang, we just do not know.