I'm a student, and could definitely be wrong on this, but my take is this:

Up to speed Va: MAXIMUM control deflection will NOT break the airplane. You can yank-n-bank, and the airplane will still be intact.

Above speed Vno: Flying straight-n-level is okay, but LESS than full control deflection might break the airplane. Minor control input, or even surprise turbulence (with no control input) could conceivably break the airplane.

Of course, I'll defer to more experienced voices here.

**edit:** fixed my description of Vno as Ewfflyer pointed out I had Vno in the wrong spot.