why is 0.25 a quarter but 0.5 is a half? why isnt half 0.50
0.5 is exactly the same as 0.50, 0.500, 0.5000, 0.50000 and any other way you wish to write it
The . is the decimal point and when people say "to two decimal places" or "three decimal places" refers to how many numbers you quote after the decimal point.