The idea is simple yet almost unfathomable. Everything in reality we see is just what our brains are programmed to interpret reality as. The computer or phone screen you are looking at right now only appears and feels the way it does because that is the best way for out brains to understand what it actually is.
Confused? Professor Donald Hoffman at the University of California, Irvine offers a helpful metaphor for wrapping your head around the concept. Imagine a folder on the desktop of your computer. In that folder you know there are files, but you know that folder itself is not the files. It is simply a visual representation of where and what the files are. So in that same sense, he suggests that every object we see is simply a representation of true reality, just like the folder.
Check out Professor Hoffman's mind-boggling TED Talk where he goes into detail on this concept below: