You can picture this like branches on a tree - you choose a peanut butter and jelly sandwich for lunch today, but in a divergent world, maybe you choose ham and cheese. The worlds branch off and continue to branch off forever, exploring all possible outcomes of chance.
As far as I understand physics (which is not much), I don't know whether it is or will ever be possible to know whether this many-worlds hypothesis (or any multiverse hypothesis) is true. But if it is, it creates some interesting food for thought.
For example, every time I narrowly avoid a car accident, another Val does not avoid that accident. Maybe she walks away, maybe she doesn't. There would be real worlds in which I was never born, or I died when I was young, or died yesterday - and if you pull all of these universes together and compare them day by day, each day there are fewer and fewer Vals. When you think about it that way, you get to thinking that maybe we live in the best of possible universes, because at least those of us who are having this discussion are still here.
But on the flip side, think of what we are missing in this world that would still exist in others. In one branch, JFK is not shot. In another, maybe Lenin never makes it back to Russia and the Communist Revolution never happens, saving millions of lives. (You can see how this line of thinking makes authors of historical fiction AND science fiction drool...)
And in still other branches of less global significance, my dad is still alive.
I enjoy thinking that some other Val is getting to spend time with him and watch him retire and grow old. I enjoy thinking that in another world, all of his as-yet-unplanned metal sculpture creations have become a reality. These other Dads would get to do all the things we will miss doing with him in this world. This actually comforts me far more than any notions of an afterlife, which are similarly unknowable but somehow more mystical.
If you lay all of the universes on top of each other in a Subtle Knife kind of way, maybe you are passing by your loved ones as you walk down the "same" street. When you enter your childhood home, maybe your family is still there in some other universe, and you can feel the warmth and happiness drifting through between the layers.
And maybe, if you tried hard enough, you could hear the sound of their laughter.