8.1.1 Using the TMDb API

TMDb’s API is accessed by constructing a RESTful URI for the appropriate function, such as “search for movies matching a keyword” or “retrieve detailed information about a specific movie”. To prevent abuse and track each user of the API separately, each developer must first obtain their own API key by requesting one via the TMDb website. Request URI’s that do not include a valid API key are not honored, returning an error instead. For request URI’s containing a valid API key, TMDb returns a JSON object as the result of the request encoded by the URI. This flow—construct a RESTful URI that includes an API key, receive a JSON response—is a common pattern for interacting with external services.

source