Not to worry. Physicists don't understand it either. It is known to be true based on compelling evidence, just as quantum mechanics is, but it isn't something that you can really comprehend.
An insight that may help though is how you perceive scales, sizes and properties of materials isn't at all how they really are. As an example, you think of your desk as a solid object because that is how you, as big as you are and with the senses you have, perceive it. But on the level of atoms that same desk is overwhelmingly, and I mean overwhelmingly, empty space. How we perceive the world with our senses simply isn't how the world is and that is a big part of why we don't comprehend many things.