ForwardAction is a dummy action (included in struts extras) that does nothing but forward the request to a page defined in the parameter attribute. The forward tag defines a forward for the action. An action can have several forwards to choose from between them. The definition of the forward attribute is below, copied from the DTD documentation
Module-relative path of the servlet or other resource that will process this request, instead of the Action class specified by "type". The path WILL NOT be processed through the "forwardPattern" attribute that is configured on the "controller" element for this module. Exactly one of "forward", "include", or "type" must be specified.
An ActionForward represents a destination to which the controller, RequestProcessor, might be directed to perform a RequestDispatcher.forward or HttpServletResponse.sendRedirect to, as a result of processing activities of an Action class. Instances of this class may be created dynamically as necessary, or configured in association with an ActionMapping instance for named lookup of potentially multiple destinations for a particular mapping instance.
An ActionForward is represented by the forward tag in the struts config, and it's the return of the execute method in the Action class