Out and Ref in C#

Here is the explanation from the book

Ref parameter
Variable values are given in the Main() method but can be altered by a method call.

Out parameter
Variable values are not given in the Main() method but can be obtained by a method call.

The way I understood. But I am not an adept in C# therefore my explanation is questionable.

//Reference Parameter

using System;
public class ParameterDemo2
{
public static void Main()
{
int var = 4;

Console.WriteLine("In Main var is {0}", var);

MethodWithRefParam(ref var); //calling method with a reference parameter

Console.WriteLine("In Main var is {0}", var);
}
public static void MethodWithRefParam(ref int parm)
{
parm = 888;
Console.WriteLine("In MethodWithRefParam, param is {0}", parm);
}
}
/*
In Main var is 4
In MethodWithRefParam, param is 888
In Main var is 888 //Note that var value has been changed after method call
*/

//Out parameter

using System;
public class InputMethodDemo
{
public static void Main()
{
int first, second;
InputMethod(out first, out second); //notice use of out

Console.WriteLine("After InputMethod first is {0} and second is {1}", first, second);
}
//notice use of out
public static void InputMethod(out int one, out int two)
{
string s1, s2;

Console.Write("Enter first integer ");
s1 = Console.ReadLine();
one = Convert.ToInt32(s1);

Console.Write("Enter second integer ");
s2 = Console.ReadLine();
two = Convert.ToInt32(s2);
}
}
/*
Enter first integer 2
Enter second integer 4
After InputMethod first is 2 and second is 4
*/

/*
Note that values for var are not given in the Main() method but obtained by a method call
*/