Device registration associates a device or app installation with an account, licence or service record under a particular system. It can use an identifier, key or other verification process. Registration is separate from local Wi-Fi connection and may be separate from active playback limits; a listed device is not automatically permission for another concurrent stream.
A practical example
A customer replacing a television may need a publisher's supported licence-transfer procedure as well as service setup on the new screen. Those steps can involve independent systems, so removing an old Wi-Fi connection alone does not necessarily complete either account change.
A common misunderstanding
Do not assume registrations transfer automatically after reinstalling or resetting equipment. Keep necessary records private and confirm the supported transfer process before deleting the working installation or account details.
Related terms
General operational definition; actual service terms remain separate. Editorial approach