What's the difference between these data types; float and double.

Answer 1

As the name implies, a double has 2x the precision of float.
The float data type is a single precision 32 bits.
The double data type is a double-precision 64-bit.

Answer 2

A double is 64 and single precision (float) is 32 bits.
The double has a bigger mantissa (the integer bits of the real number).
Any inaccuracies will be smaller in the double.