ActionResult
ActionResult is a fundamental concept in ASP.NET MVC and ASP.NET Core MVC, representing the result of an action method's execution. It serves as an abstraction for the various types of responses that can be returned from a controller action to the client. Instead of directly writing to the response stream, action methods return an ActionResult object, which encapsulates the logic for how to generate the HTTP response.
Common implementations of ActionResult include content results like JsonResult for JSON data, ContentResult for plain text
By returning an ActionResult, controllers delegate the responsibility of constructing the HTTP response to the framework.