Simple definition
The WordPress REST API exposes site resources through JSON endpoints with permission checks.
Purpose and use
The WordPress REST, Representational State Transfer, API exposes HTTP resources to read or modify content and objects made available through its routes.
How does it work?
Endpoints use methods, JSON representations and context-appropriate authentication; selected public-content reads require no sign-in.
Example and verification
For an integration, verify permissions per operation and test authentication and access failures on private resources.
Points to watch
A route's existence does not imply that all content is public. Custom endpoints must enforce permission checks on the server.
In short
The API supplies an integration channel whose security depends on actual route contracts, permissions and validation.