In Spring MVC, the "initBinder" method is used to initialize WebDataBinder objects. WebDataBinder is used to bind request parameters to controller methods. The initBinder method takes a WebDataBinder object and an HttpServletRequest object as arguments. The WebDataBinder is then used to bind the request parameters to the controller method.   For example, if you have a controller method that takes a Person object as an argument, you can use the initBinder method to bind the person's name and age request parameters to the Person object.   This is useful when you want to automatically populate form fields with data from a database or other source. It can also be used to pre-process request parameters before they are passed to the controller method.   The initBinder method is called before the controller method is invoked. It is important to note that the WebDataBinder object is only used for binding request parameters. It cannot be used to bind other objects such as model attributes.  To use the init binder annotation, you first need to create a custom editor class that extends the PropertyEditorSupport class and overrides the setAsText() method. This method will be called whenever the user enters data into a field that is mapped to the type specified in the editor class.  Once you have created the custom editor class, you can annotate a controller method with the @InitBinder annotation and specify the type that this method should handle. The init binder annotated method must have a single argument of type WebDataBinder. This object provides methods for registering custom editors.