Quantum Mechanics works by assigning probabilities to outcomes, instead of stating exactly when or where something will happen.
A common example is Schrodinger’s cat thought experiment.
This says that if a cat is placed in an isolated box, with a sealed container of poison that will break when some random process occurs, then from an outsider’s perspective, the cat is both dead and alive at the same time.
It is only by opening the box to check on the cat that we are able to determine what has happened to it.
In many worlds interpretation, if someone were to open the box and find the cat alive, then there would also be a split Universe where the cat is found dead.
In this case, in both Parallel Universes, there would be a copy of you, with the only difference being that one would have an alive cat and the other would have a dead one.
However, these Parallel Universes are intrinsically and fundamentally separate; we can never communicate between them.