Originating as a simple thought experiment, the idea of alternate universes and timelines has slowly gained more and more credence over the past few decades. Now, scientists and clerics alike are looking into the concept further. In the modern day, it's generally accepted that universes alternate to our own do exist and have perhaps affected us on a deeper level than we may initially think...
The theory that, much like our solar system, our universe is but a single instance of an infinitely expanding collective. In our vast universe, there is an incredibly high probability that other planets similar if not identical to our Earth exist. The same school of thought can be applied with multiverse theory. If our universe exists in an infinite void, is it not possible that there exists a universe out there among the countless others that is nearly identical to our own?
Another concept stemming from that of multiverse theory is that of infinite universes through alternate timelines. This approach is similar to the thought experiment known as "Schrödinger's cat". This theory believes that for every single decision we make, an alternate universe or timeline exists where a different decision was made. Whether the act of making the decision is what spawns these split timelines, or they simply already existed out within the void as describied by multiverse theory, the fact is that there is an infinite number of our "others" spread across the ether experiencing worlds both vastly different and uncannily similar to our own.
Each and every one of us is unique. We all have our own thoughts, opinions, ideals, and methods. However, some believe that through the multiverse, it is possible to tap into our other selves and "link" our consciousnesses across space and time. Through this method, it is said that one can travel through and experience alternate universes.