This extension, sometimes affectionately called SkinkGlue, allows other extensions to add new account types in Thunderbird. Currently, this is used at least by the ExQuilla and TweeQuilla extensions. It is typically installed along with those other extensions.
This extension does nothing by itself, but provides critical glue between other extensions and Thunderbird when new account types (like Twitter or Exchange Server) are needed. There are no user interface changes associated with this extension.