I am trying to enable cross origin resources sharing on my ASP.NET Core Web API, but I am stuck.

The EnableCors attribute accepts policyName of type string as parameter:

// Summary:
//     Creates a new instance of the Microsoft.AspNetCore.Cors.Core.EnableCorsAttribute.
//
// Parameters:
//   policyName:
//     The name of the policy to be applied.
public EnableCorsAttribute(string policyName);

What does the policyName mean and how can I configure CORS on an ASP.NET Core Web API?