Float vs. Double

Question

I don't know the difference between both. just know that their values may vary after some decimal points even if you assign both same value after decimal point. maybe I'm wrong. please tell all the differences between both and when should I use either and why?

Answer 1

one difference of size
Float occupies: 4 bytes
and
Double occupies: 8 bytes

Answer 2

Float holds decimal values, up to 4bits size, and Double holds up to (duuh) double the size, 8 bits.
Float holds numbers with up to 7 decimal digits, while double holds up to 15 decimal digits