C# の再帰的メソッド呼び出しとは何ですか?

if (p!=0) { return (n * power(n, p - 1)); }

using System; using System.IO; public class Demo { public static void Main(string[] args) { int n = 5; int p = 2; long res; res = power(n, p); Console.WriteLine(res); } static long power (int n, int p) { if (p!=0) { return (n * power(n, p - 1)); } return 1; } }