c# 语句问题求解（新手），代码如下

       Console.WriteLine("Enter a Number:");
        double firstNumber = Convert.ToDouble(Console.ReadLine());
        Console.WriteLine("Enter another Number:");
        double secondNumber = Convert.ToDouble(Console.ReadLine());
        string Comparison;
        if (firstNumber > secondNumber)
            Comparison = "more than";
        else
        {
            if (firstNumber < secondNumber) 
            Comparison = "less than";
            else
            Comparison = "equal to";
        }
        Console.WriteLine($"the first Number is {Comparison } than the second Number.");
        Console.ReadLine();
代码的倒二语句中$的含义，以及Comparison为什么要加花括号？

Console.WriteLine($"the first Number is {Comparison } than the second Number.");
这是C# 2015新的语法，相当于
Console.WriteLine("the first Number is {0} than the second Number.", Comparison);