Explain this program please?

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Sample
{
class Program
{
static int Pow(int x, int y=2)
{
int result = 1;
for (int i = 0; i < y; i++)
{
result *= x;
}
return result;
}
static void Main(string[] args)
{
Console.WriteLine(Pow(6));

Console.WriteLine(Pow(3, 4));
}
}
}