The Account plugin basically allows you (as the site admin) to give your users a "My account" page. It also tries to serve as the hub of the site to which plugins can add their own action links.
What is an action link?
An action link is simply an HTTP link that allows the user to perform an action. Examples of possible actions could include something like:
"Connect an OpenID account to your site account"
It is entirely up to other plugin developers whether or not they choose to support this plugin as a hub. The plugin itself comes with few if any actions.