Now to start explaining, you know when you see a tree and you follow it up and eventually it breaks off the trunk into smaller branches? Imagine the tree represents you, the break were the smaller branches come apart signifies a decision in your life that you either take or refuse, and the smaller branches - they signify who you are depending on your reaction to the decision. And to think of it like a tree is a pretty good explanation, because trees have branches that come off branches off branches and so on.

FOR EXAMPLE:
Sally has lived her live normally, until one day she is offered a big job as anexecutiveproducer at a big TV station.
(a) she could except the job and go on to become a very rich, well known producer.
(b) she could refuse the job and go about her life and perhaps chose to do something else that could benefit her life. And:
(c) she could ignore the offer and spend her life wondering what she might have done, which could lead to depression etc.
^^They are exampled of 3 different parallel universes.

Some people believe that instead of having a different universes for a single person and every decision they ever make in their life, they are grouped together.
FOR EXAMPLE: If Sally had taken option (c) and had perhaps become depressed, then her universe would be full of depressed,unachievablepeople. This world is altered a lot, not just through Sally's decision, but if everyone in her world were lazy or dumb people then perhaps her world would not be as developed as modern day society today.

If Sally had taken option (a) and became very rich and famous, her world may be full of rich high-achieving people who all had high-paying jobs. Perhaps this world would by highly enriched with technologies of the future (e.g. hovercrafts,) because the people of this 'Parallel Sally''s world would all be confident, academic people who had the potential to strive for cures for cancer etc.

On another idea, some people believe it is possible to travel back and forth between these Parallel Universes using a type of time machine. This is where the idea that 'The distinction between thepast, present andfutureis only a stubbornly persistent illusion,' said by Albert Einstein. But we may never truly know.

I hope this has opened your mind, please feel free to inbox me your thoughts and/or creative criticism :)