Regarding enabling CORS in web api project

i was just looking at this article https://www.asp.net/web-api/overview/security/enabling-cross-origin-requests-in-web-api to know how we can enable CORS for web api.

the article show how to enable cors. here is code

public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // New code
            config.EnableCors();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }

1) my question is config.EnableCors(); is not capable to enable CORS because article show we need to decorate controller or action

enable cors for single controller.

[EnableCors(origins:"http://www.example.com", headers:"*", methods:"*")]publicclassItemsController:ApiController{publicHttpResponseMessageGetAll(){...}publicHttpResponseMessageGetItem(int id){...}publicHttpResponseMessagePost(){...}[DisableCors]publicHttpResponseMessagePutItem(int id){...}}

Enable cors for single action.

public class ItemsController : ApiController
{
    public HttpResponseMessage GetAll() { ... }

    [EnableCors(origins: "http://www.example.com", headers: "*", methods: "*")]
    public HttpResponseMessage GetItem(int id) { ... }

    public HttpResponseMessage Post() { ... }
    public HttpResponseMessage PutItem(int id) { ... }
}

guide me about this syntax

 [EnableCors(origins: "http://www.example.com", headers: "*", methods: "*")]

origins: url : do i need to provide here any valid url or any url ?

what is the meaning of headers: "*", methods: "*"

thanks