"0" or "Zero" is normally seen as "nothing", but "0" refers specifically to having "0" amount of something as a value, as opposed to "nothing" which refers to the
non-existence of something, whether it's a quantity or not.
The symbol of "0" is resemblant of the letter "O" but taller and thinner, for this reason, when used digitally it is common for an alternate version of this symbol with a diagonal line from
bottom left to top right of the shape to be used, for it
not to be confused with the letter "O".