authority
the authority component; who speaks for a host
the part of a URI naming who is responsible for the resource (host + optional port), and the question of whether a connection is entitled to answer for it
The authority component of an http/https URI is host[:port]. But the deeper question RFC 9110 §4.3 tackles is authoritative access: given a URI, which server connection is allowed to answer for it? For https, that's settled by the TLS certificate matching the host. For http, by DNS plus the connection. This is where 2818 (HTTP Over TLS) folded into 9110 — the certificate-identity rules now live in the core spec.
How it is read
RFC 2818 — HTTP Over TLS (2000)
spec
The original home of the "check the certificate's subjectAltName against the URI host" rule. Informational, and for two decades the de facto source everyone cited for HTTPS identity.
RFC 9110 §4.3.4 (2022)
spec
Obsoletes 2818 and moves HTTPS identity verification into the standards-track core: the client MUST verify the service identity using the process in RFC 6125, matching against the URI's host. HTTPS identity is no longer a side document.