forward() method of RequestDispatcher is a server side activity. So the request and its associated session are available to the forwarded resource.This method is normally used for sending a request and response object to resources (
servlets or
JSP's)which are in the same ServletContext.
sendRedirect() method of a response object sends the url(parameter of sendRedirect() method) to the browser and the browser sends a new request to that url. sendRedirect() used to forward requests to a resource which is outside of the current web application. It is like ,opening a new browser and type your url.
correct me if i am wrong.