Or,if you really simplify it,a standard piano is tuned in a very particular way and has a set of possible notes.With micro tuning you can totally break away from this.
Imagine you make your own piano selecting what notes you want,maybe your piano only has 4 keys,maybe your piano has 50 keys,maybe your piano has no octaves at all,maybe your piano splits an octave into 21 notes instead of 12.This is what micro tuning can do for you.