Single sign-on lets your team reach the helpdesk with the work account they already have, instead of a separate Raiseaticket password. It is part of the premium Microsoft 365 or Google Workspace integration rather than something bought on its own.
No. Single sign-on comes with the premium integration for Microsoft 365 or Google Workspace. If you take either integration you get single sign-on with it, along with everything else in that integration - so there is no separate SSO product to price up.
An administrator account on the identity provider - for Microsoft 365 that means an Office 365 administrator - because the connection has to be authorised at the directory level. The configuration itself is done from your portal settings by a Raiseaticket admin, and the Office 365 setup is automated from there rather than requiring manual key exchange.
See what information is required for the Office 365 integration for the exact details to have ready.
Two reasons, usually. The first is simply one fewer password: people sign in with the account they already use all day, which removes a common reason for support requests about the support tool itself. The second is control - access is governed by your existing directory, so joiners and leavers are handled where they are already handled rather than as a separate task in the helpdesk.
Microsoft 365 (including Outlook and Exchange) and Google Workspace (including Gmail). Both are premium integrations, and single sign-on is included in each.