Friend once said the difference between solid-state and non, was that solid-state didn't use magic crystals.
But personaly I don't like the term as it is not as clear-cut in all peoples perspectives. You could say one solid-state is digital and non solid state is not 100% digital. Though some would also argue that digital is mearly a perception of measurement in a analogue World.
I'll let you read the wiki on it and draw your own conclusions:
http://en.wikipedia.org/wiki/Solid-state_(electronics)
But personaly I don't like the term as it is not as clear-cut in all peoples perspectives. You could say one solid-state is digital and non solid state is not 100% digital. Though some would also argue that digital is mearly a perception of measurement in a analogue World.