protected packages on emerge clean

[leachbj]

I've been searching for information on how packages are deemed as protected during an "emerge clean".

Is there a simple definition?

Assuming they are protected becuase some other package is dependent on them - can the portage tools show these dependencies. If its a case of simply re-emerging these dependent packages so I can do a proper clean that would be nice to know.

cheers,
bern.