An introductary small problem

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C#

Visual-Studio

VS2012

// Namespace Declaration
using System;

// Program start class
class InteractiveWelcome
{
    // Main begins program execution.
    public static void Main()
    {
        // Write to console/get input
        Console.Write("What is your name?: ");
        Console.Write("Hello, {0}! ", Console.ReadLine());
        Console.WriteLine("Welcome to the C# Station Tutorial!");
    }
}

I was just trying to learn C# language an i noticed that unlike C++ its Main() function includes an additional class wrapped around it! So i am wondering is it necessary to define an class wrapping Main() func or declaring it without that class will too be fine!

Another thing i noticed that its Main() func consists of public static keyword , i know the meaning of public but whats the use? i mean to say that why are we declaring public as the main() function should be already available to all the code{ global scope}. I couldnt any succesful answer from any E-book, so anybody could help me try to understand them!!