What means a point after new class()

Question

Hello,

may be this is a very simple question, but I can't find any answer. To initialize a class to an object I know some ways for new, like this

 

 class A;      //for short I don't define A

 

 A a = new A();

or

 A a = new A(1, "nnn");

or
 A a = new A()

   {

      x = 1,

      s = "nnn"

   };
or "anonym" 

var pet = new { x = 1, s = "nnn" };
 

but what means this point "." in the example downstairs after "new WebHostBuilder()" ?

var host = new WebHostBuilder()
        .UseKestrel()
        .UseContentRoot(Directory.GetCurrentDirectory())
        .UseIISIntegration()
        .UseStartup()
        .Build();

 Thank you if some would explain me that.