The conditional expression entered for the image sets the image to show a different icon depending on whether you are authenticated (logged in) or not. You selected the image source file twice to copy both image files into your project.
The conditional expression entered in the next step for the Go Link sets the text of the link to
Logout if the user is authenticated,
Login if not.
This expression sets the destination of the link to call the ADF authentication servlet, which is the standard way to handle login and logout. Different parameters are passed depending on which action is required: logout if the user is authenticated (logged in); and login if the user is not authenticated. The login action automatically redirects to the login page, then to the page specified by the success_url parameter (
products.jspx in this case). The logout action redirects to the page specified by the end_url parameter (