Takes one back-channel logout request from the transport and answers it: reads the logout_token out of the posted form, puts it through the receiver's profile, hands the notification to the application, and shapes the response (OpenID Connect Back-Channel Logout 1.0 Sections 2.5 and 2.8).
What a back-channel logout request earns: the status code the transport answers with, and - only beside a 400 - the error body the provider reads (OpenID Connect Back-Channel Logout 1.0 Section 2.8). The shape is transport-neutral on purpose: any host adapter renders it, none decides it.
What a back-channel logout receiver expects of every Logout Token: the provider it talks to as the issuer, its own client identifier as the audience, and the clock tolerance it allows.
Where validated logout orders land: the application's half of the receiver, called once per accepted Logout Token with the notification already carrying its provider's authority.