You are starting to get the hang of this aren't you? Good, because we are going to switch gears for a second. This will your first plugin that modifies the Movable Type user interface a bit, specifically Movable Type's login screen.

OpenID is a decentralized authentication protocol that allows systems to delegate authentication and registration to a third party.

Ok, now in English.

OpenID is a feature that allows people to login into Movable Type without having to create a username and password. Instead, users login to Movable Type via a third party like Flickr, Yahoo, AOL, etc.

Movable Type has built in support for OpenID thereby allowing readers to authenticate against any OpenID endpoint in order to leave a comment.