Hosts and services
The hostnames the server knows and the services attached to each, across all accounts and the system; the Hosts and Services screens, and host:*, service:list, service:refresh, service:remove and host:remove-dangling.
How DNS publication works
The server's own name servers, how a change travels from a service to the name servers in the background, DNSSEC and the zone's SOA, the self-repair that runs on timers, and dns:publish-pending, dns:republish and dns:inspect.
DNS Records
The DNS Records screen across all accounts, the four kinds of record in a zone and who may change each, temporary records and dns:add-temporary-record, and the record maintenance commands.
DNS Publication Failures
The DNS Publication Failures screen, the zones that are behind without a recorded failure, the four kinds of backend failure and who sees each, the common causes, and dns:error-log:notify and dns:error-log:prune.
Shared IP Address Groups
What a shared IP address group is, how accounts are assigned to one, the Shared IP Address Groups screen and the certificates for the addresses, ip_address_group:*, adding a group after install, and the accounts' private addresses.
DNS backends
Where a zone's records are published: the built-in name servers, another PowerDNS, Cloudflare, deSEC, or a provider the account holder updates by hand. What each needs and gives up, the mirror on the server's own name servers, and how a zone's backend is chosen.