Many applications require users to log in supplying a username and a password before they can access the application or perform certain functions. Common examples where a log in is required include email applications, a Windows log in, and most web-based applications that store any personal information. Users don't want to log in to an application, what they want is to perform some task or get access to some data. The tasks and data are completely application-specific. When I log in to my email client it's not because I want to log in it's because I want to read or send email. It's a pretty obvious fact but it's important to pay attention to because the act of logging in with a user name and password have become a such a common part of daily life that many people experience Password Fatigue - a condition that results when people are required to remember many passwords as part of their daily living.
Many attempts have been made to handle consolidation of user identification across websites such as OpenID. This is not a simple problem to solve. The case is different where you have several applications that all belong to one organization. If all the users and all the applications are run by the same person, company or organization then why have many different user names and passwords? All of a user's passwords and usernames can be stored in one trusted source that meets the requirements of the most demanding application. This concept is called Single Sign-On (SSO). Single Sign-on means that a user can log in one time and have access to many applications for that session. SSO can reduce the number of logins and passwords that a user has to remember from twenty or more all the way down to just one.
Like I said at the beginning, users don't log in because they want to log in. They log in to get access to some data or function that the application has. With SSO the user logs in to the computer then they can just open their email without a password. They can access company websites and web applications without a password. They can use time sheets applications, accounting applications, company directories, internal instant messaging and company database applications all without remembering one more password and without compromising data security. This is more than just convenience, it simplifies workflows to enhance productivity. It enhances moral and reduces the moments where users pause and curse an application. It lets users follow directives to choose strong passwords that they can remember because there's only one.
Single Sign-On is not nice to have. It is essential for any business that wants to grow and retain loyal employees.