What does "Keep me signed in on this computer unless I log off" do?

After you sign in, if you close your browser or after a period of inactivity, your password will expire. But for your convenience, you can choose to save your User ID and password on this computer. Your password will be saved even if you disconnect from the Internet, close your browser or turn off your computer. Your password will be saved until you explicitly log off. You have to have cookies enabled in your browser in order to be able to use this feature. As a safety measure, if you are using a public computer or shared computer, you should always log off when you are done and not use this feature.