oAuth is an open protocol for secure user authentication across APIs. It allows users to gain limited access to websites by using their Twitter credentials. It's a very sound method of user authentication, and doesn't take too much work to get going. Twitter oAuth is used by hundreds of third-party Twitter clients and mashups—just to give you an idea of how useful it can be.
Getting used to how Twitter oAuth works takes a little time.
When a user comes to your login page, you send a GET
request to Twitter for a set of request codes. These request codes are used to verify the user on the Twitter website.
The user then goes through to Twitter to either allow or deny your application access to their account. If they allow the application access, they will be taken back to your application. The URL they get sent to will have an oAuth token appended to the end. This is used in the next step.
Back at your application, you then send another GET
request for some access...