If on, then users will see both manual and a SAML login button. If off they will always be taken directly to the IdP login page.
If passive, then the users that are already authenticated into the IDP will be automatically logged in, otherwise they will be sent to Moodle login page.
If off, then admins can still see the manual login page via /login/index.php?saml=off
If on, then external pages can deep link into moodle using saml eg /course/view.php?id=45&saml=on
If set to test IdP connection, the network will be checked for connectivity, and if functional, SAML login will be initiated.