What is SSO ?

SSO stands for Single Sign On. Normally when we are implementing authentication in ASP.NET web application, you have to create a login page for each of your applications. Imagine that you have two or more web application which are related together. So you may want to use a mechanism which allows you to create just one login page for all your related applications. In this way, once you have logged in you can browse other application without any extra login required. Single sign-on (SSO) is a method of access control that enables a user to authenticate once and gain access to the resources of multiple software systems

SSO allow you to accomplish the goal of Cross Application login. In other words, we just want to have one login page for whole web site, and once the users have been authenticated they can browse to other web sites, without the need to re-login.