You can learn more about Coach DeMeo here from an article at American Football Monthly.
I'll go back over the coaching points in the diagram.
In a nutshell, the QB reads the DE as the FB flares out and throws to him if the DE rushes or squats. He will only move to his #2 if the DE jumps the swing route of the FB.
The middle screen portion is just as you would expect. The line should momentarily stop the charge of the defensive linemen before going to second level... The Split End takes a big step downfield then comes back down the LOS - getting behind the D line and looking for the ball from the QB. The HB is also running a swing route and he is eyeballing the CB over the SE. If the CB jumps the screen, he immediately calls "Ball" and the QB should hit him in the flat.
That's it. It sounds complicated, but as his video shows, all it takes is a good practice routine filled with plenty of reps.
I'm posting a link to my original Triple Screen notes (in Adobe PDF format) here. This also shows how he runs it from the flexbone formation using some wingback motion.