static keyword in C# class method

using System;

namespace TestFile
{
    class Program
    {
        static void Main(string[] args)
        {
            var result = Calculator.Sum(5, 7);
            Console.WriteLine("The sum of 5 and 7 is " + result);
        }

        
    }

    public static class Calculator
    {
        public static int Sum(int a, int b)
        {
            return a + b;
        }
    }

    
    
}