in second one , why is that "(x = {0} , y = {1} );

Question

please help me understand

Answer 1

Console.Write("I am {0}, and my age is {1}, {2}", name, age, greeting);

// The {x} is a place holder for a variable. It's just another way instead of using "I am + name + ", and my...
// And as the rules follows, the first index = 0, second = 1, third = 2, etc... etc...

Answer 2

Console.WriteLine("x={0} y={1}",5,10);
// it's print x=5 y=10
0 inside the curly brace is value after ", and so on.