In the example, call the function Calculate
Calculate(15, 7, function (value1, value2)
     {
            return value1 + value2;
     }
);

Attention! Unnamed function marked in blue

In the function Calculate
1st parameter pass the number 15
With the 2nd parameter we pass the number 7
With the 3rd parameter we pass the function without a name
function (value1, value2)
{
     return value1 + value2;
}

value1 1st parameter of the unnamed function
value2 2nd parameter of the unnamed function