Float and double are both widely used data types in programming that have the ability to store decimal or floating-point​ numbers. The only difference between them is the precision. 

A float is a 32-bit IEEE 754 single-precision floating-point number. 
>  `1 bit` for the sign `8 bits` for the exponent `23 bits` for the value. 

A `float` has 7 decimal digits of precision and occupies `32 bits`.



A double is a 64-bit IEEE 754 double-precision floating-point number. `1 bit` for the sign, `11 bits` for the exponent, and `52 bits` for the value. A double has 15 decimal digits of precision and occupies a total of `64 bits`.



Below is example for further clarification. See how `float` cannot store the entire value since it has less precision than `double`. 

using System;
 
class HelloWorld
{
    static void Main()
    {
        float f = 1F/3; //1F is float value of 1
        double d = 1D/3; // 1D is 1 stored as a double
        Console.WriteLine("float: {0} double: {1}", f, d);
    }
}

What is the difference between float and double?

Float is a 32-bit single-precision, while double is a 64-bit double-precision type.