DOUBTS ON TEXT FUNCTIONS

What is syntax? At the time of "Substitute function" we used formula =substitue(cell value,CHAR(160),"") why we used CHAR(160) here? Will it differ from data to data or is it the formula? Even after using the substitue function in my worksheet the no.of characters is showing the same after applying len function, there is no change in the no.of characters even after successfully applying the formula. What is the reason? How to solve it? ATTACHED SS OF EXCEL FOR REFERENCE