WordPress MU

I'm trying to figure out what this exactly means and how to leverage it? On the 'Network Options' page (Super Admin > Options) there is a radio button to either "Maintain a global list of terms from all sites across the network." or "Disabled".

If I choose "Maintain a global list of terms from all sites across the network." what does this do and how do I use it? Does it just grab a list of all tags/categories used on all sub-blogs throughout the entire MU install?

How would I print this list out?

Even better: is it possible to use these terms to query posts from the sub-blogs individually?

Thanks!

It's in there for legacy reasons and for exisiting plugins & setups that rely on it.

All it does is maintain a global table of terms. that's it. Anythign you want to then use it for has to have a plugin written.

Does sitewide tags use this table, for example?

Thanks!

No, it does not.