What are Registered Servers?
Registered Servers are a simple way to create a pool of servers on private and public cloud that can be used on any stack and configuration. Applications can be deployed across a hybrid of cloud and registered servers, in this way you could have a dedicated server for your database and burst cloud servers for your front end.

• Using your own servers with Cloud 66: https://help.cloud66.com/rails/how-to-guides/deployment/registered-servers.html#overview