There are a few good analogies I’ve heard to help explain this concept.
“Picture a wave. In the ocean. You can see it, measure it, its height, the way the sunlight refracts when it passes through. And it’s there. And you can see it, you know what it is. It’s a wave.
And then it crashes in the shore and it’s gone. But the water is still there. The wave was just a different way for the water to be, for a little while.” (Quoted from The Good Place)