I am not a computer scientist so my understanding is "incomplete". I thought it stood for polynomial and non-polynomial time. But i do mix them up here and there. What i have read time and time again is that: If P≠NP would mean some problems really are harder to solve than to check (which feels intuitive given working encryption exists and all the mathematical functions that I know and understand). For example checking the roots of polynomials is easier than finding them in the first place.