Help Shape WordPress 2.9

The feature priority survey for WordPress 2.9 has been published on the WordPress development blog enabling users to pick and choose which features they would like to take higher priority over others. Results of the survey will not be published however, the anticipated feature list for WordPress 2.9 will be later on in July.

There was one question in the poll that had me scratching my head.

Every time I think I have this term canonical plugins figured out, I read something which throws my understanding out of the water. So far, my understanding of the term is that these plugins would be recommended so to speak where a number of people would be contributing to these particular plugins. However, when I read the answers to the question seen in the image above, I start to think that canonical plugins are blocks of functionality that instead of being directly in core, are actually just a plugin. In fact, I do a great job confusing myself trying to think of what the heck this all means.

So now, I have no idea what canonical means. Can someone help me out?