The steps are :-
(1) Open the url for example(www.testing.com)
(2) Login page opens.
(3) User enters user name and password and submits these to the server.
(4) Server validates the credentials and if valid, creates an authentication cookie and sends it back to the user browser.
(5) With valid cookie, user no longer needs to enter a user name and password to access the site on each page request.
(6) From next time he/she is simply redirected to the default page.