I am not going to explain it to you in detail I simply can't! But I will try my best to do so, I hope this sparks a interest in it makes you go and research it some more cause it truly is fascinating!
Basically imagine you where in a video game and the programmer gave you free will, you would think that the world you are in is real and would go about your normal life thinking you are in a real world. Obviously it is more complicated than that but that describes how it is.
Now how do we know this is happening and not just a theory? There are lots of things in science and physics that point to us being in a simulation and the evidence is compelling you can not dismiss it. I truly think that we may be in a simulated world however I don't think we'll ever know if we are for a sure. I really have described this terribly but if you want to see more simply google "is the world a simulation?" beware you will lose yourself for hours reading and watching videos about it!
