ORPHAN vs. IMBALANCE

[David T.]

Could someone explain to me the difference between ORPHAN and IMBALANCE accounts in GnuCash? 
Under different circumstances, GnuCash creates these accounts, and I honestly don't understand what the differences are meant to be. 
I searched the list archives, and saw Derek's 2011 response in http://lists.gnucash.org/pipermail/gnucash-user/2011-September/041127.html, but I honestly don't understand his explanation of the circumstances under which one is chosen over the other.
Is the difference significant, or would it be possible to eliminate one of these accounts from the software?
Thanks,David