RFC documents contain technical specifications and organizational notes for the Internet.
RFC originally stood for “Request For Comment”, but these documents have transcended that definition and now are simply referred to as “RFCs”.
RFCs typically define the foundational technologies of the Internet such as addressing, routing, transport and now extends to many protocols, practices and architectures such as TLS, WebRTC, JWT and OpenID Connect.
RFCs are not standards by default and can just be recommendations, proposals or shared concepts and information.
RFC 1918: Defines the address ranges for private addresses (i.e. private networks). Specifically: