Ports
Ports are interfaces the core owns; adapters are implementation details outside the core vocabulary.
Module 2 introduced the port as the boundary between core and adapter. In the vocabulary it takes its place as a first-class word: a port is an interface the core owns and the outside implements — the repository to access the database, the email sender to send email through Amazon SES.
The component-level point worth keeping is simple: ports belong to the core’s vocabulary, adapters do not. The core says “save a workspace”; which database and how, which email provider, is never the core’s concern.