Out of the box Android: What are task groups?

[Uristocles]

In the out of the box calendar (I assume it's a standard Android thing but since this is my first foray into the Android universe I suppose it could also be the Samsung calendar or the Note II Calendar specifically) there's a task list that can sync to Outlook. What are task groups? At first glance you'd hope they synchronized to Outlook categories but that doesn't seem to be the case.

What do you use them for then?

As an aside - if categories can't be synced then is the alternative to use Google Tasks and sync with something else, ignoring the built-in Task list? (The built-in tasks list doesn't seem to sync to Google tasks).