The question of what, if anything, existed before the Big Bang is still a topic of active scientific investigation and debate. The prevailing scientific understanding is that the Big Bang marks the beginning of our current observable universe, but it doesn't necessarily rule out the possibility of something existing before it.
One popular hypothesis is that the universe undergoes cycles of expansion and contraction, with each cycle beginning with a Big Bang and ending with a Big Crunch. In this scenario, the universe expands, reaches a maximum size, and then contracts back to a singularity, which then triggers another Big Bang and a new cycle begins. However, this is just one proposed idea, and it has not been confirmed by direct observational evidence.
Another possibility is that our universe is just one "bubble" or part of a larger multiverse, where each bubble represents a separate universe with its own set of physical laws. In this case, the Big Bang would correspond to the creation of our specific bubble, and there could be other bubbles with their own distinct histories outside of our observable universe.
It's important to note that these ideas are still speculative, and there is currently no conclusive evidence to support any particular theory about what may have existed before the Big Bang. The nature of time itself and what conditions were like "before" the Big Bang are still subjects of active research and exploration in cosmology and theoretical physics.