Here is a BBC report on the quest to figure out what is meant by REALITY. When mixed in the context of modern physics, this is not a well-defined, clear-cut concept. Now, this is about one hour long, but really interesting. Even if you only watch a few minutes, you can get a sense of what some areas of modern physics are looking at. Many thanks to (former ETHS student) John M. for providing the link for this video.