How am I logged into multiple websites even though I only logged in once?
By default, PIN creates a record of your login asserting that you have authenticated, which only lives as long as the browser with which you logged in is open. The PIN System is able to maintain your record for longer periods of time if you choose “Remember Me” when you login. It is an optional feature that you may select when you log in and only works on the computers where you enable it.
Websites typically opt to only allow a login to last for as long as you have your browser open, i.e. they are fine accepting an authentication, even though you logged into another application, as long as it happened within the same browser session. A few websites may require you to log in every time you go there. Some sites work when the “Remember Me” option is selected and allow authentications from previous browser sessions, irrespective of the site you accessed then, but typically have a time limit after which you will still need to login again.
When you logout of PIN, the record of your login is deleted.