Imagine silence – the absence of all noise and sound. Strain as much as you like your ears cannot detect anything.
This is Nothing.
Now you hear an orchestra begin to play a concerto. It starts softly, the strings, the woodwind the percussion and brass building in layers. The music steadily gets louder. Another orchestra starts to play another concerto. Over time more and more orchestras join in, each playing there own concerto. The noise builds and builds to a cacophony of tones, rhythms, chords and progressions. It gets louder and louder. The waves of sound crash together. The sound is so overwhelming that you hear nothing. You cannot make out a single note, beat or melody because the noise has become so complete.
This is everything.
In everything you hear nothing; everything is the same as nothing.
They are two opposites that unite and share a perception. Entirely different, but entirely the same.