Picturepark IDS (short: PIDS) is the Picturepark Identity Server, which serves as the default trusted Identity Provider of your Picturepark Content Platform. All identity information (e.g. user attributes) are saved in the Picturepark IDS. You can access multiple Pictureparks with the same identity.
Whenever Office 365 needs to verify a user, for example, Azure AD performs all identity and access management and is thus the trusted identity provider.