If you think you understand what 'reality' is, then you don't. But BBC's Horizon team gave it a shot anyhow: "What is Reality?"
There is a strange and mysterious world that surrounds us, a world largely hidden from our senses. The quest to explain the true nature of reality is one of the great scientific detective stories.
Clues have been pieced together from deep within the atom, from the event horizon of black holes, and from the far reaches of the cosmos. It may be that that we are part of a cosmic hologram, projected from the edge of the universe. Or that we exist in an infinity of parallel worlds. Your reality may never look quite the same again.
Lots of brain-bending goodness in there, tuck in.