What is Object?

Object is a real world entity, object will be existing physically which means it will occupy memory where as Class is a logical unit.

If we want to use class methods or variables we need to create object, there is no other way to use class methods without creating object.

Ex:

 class A
    {
       public int sum(int a,int b)
        {
            return a + b;
        }
    }

class Program
    {
        static void Main(string[] args)
        {
            A obj = new A(); // Creating Object of Class A to access public methods of ClassA
            int sum = obj.sum(5, 4);
            Console.WriteLine(sum);
            Console.ReadKey();
           
        }
    }

In Class 'Program' used method 'sum' of another Class A by creating object of Class A