Twitter, as with every other third-party service, uses OAuth to handle authentication and requires an authentication key to write software using their API. It's their service, so you have to play by their rules, of course.
To register a new application with Twitter, go to https://apps.twitter.com/. Then you click on the Create New App button. Since we haven't deployed the Notes application to a regular server and, more importantly, there isn't a valid domain name for the application, we have to give Twitter the configuration required for testing on our local laptop.
Every service offering OAuth2 authentication has an administrative backend for registering new applications. The common purpose is to describe ...
