Trying to explain dyslexia falls into the same category as describing colour to someone without sight, or Donald Trump to a non-American: technically possible, but not likely to be pretty. This letter-shifting website helps solve that problem.
The website works by shifting the letters in words around continuously. If you concentrate and really focus on individual words, you can understand what's going on, but it's much like deciphering a code. Given that dyslexia is believed to be associated with problems breaking down and confusing letters and sounds, it makes for a decent, if not perfect analogy.
Dyslexia affects people to different degrees, and according to commenters on Reddit, the site is a more extreme version than what they commonly see. Still, if it's just a tiny bit accurate, it shows the difficulties people with dyslexia face every day.