what is the difference between Float and Double?

Answer 1

To addition to her answer @Lara I want to add that in c# there are 3 types of not integer.
1) float with precision of 7 digits (32-bit)
2) double with precision of 15-16 digits (64-bit)
3) decimal with precision of 28-29 digits (128-bit)
However, decimals are much much slower than float/double

Answer 2

it is the same in C++, however in Java Float is 4 bytes and Double is 8 bytes

Answer 3

float is of 4 bytes and double is of 8 bytes
and one more important thing is
float can display 7 values after decimal point(called precision 7) and double can display 16 values after decimal point