Yes that's correct definition. 1 more thing which would do in Quality Center is, if any bug is postponed then along with the status 'Resolved Later', the release in which that bug would get resolved is selected. And generally high priority bugs, rather say high severity bugs should not be postponed. In out project few bugs were postponed as those were trivial, mainly some cosmetic issues and for those trivial bugs, taking another release was not of worth delaying the schedule for, hence those were marked resolved later.
Enhancement: New features or changes to the existing functionality. These would be covered as change requests.
Postpone: Mostly used for cosmetic defects which are not in priority for atleast next 3 release cycles.
Depends on how you may want to deal with defects with your existing defect management tool.
You can add a custom field in bugzilla as "Bug Type" with values as Defect, Enhancement & Deferred Items. Create a tracking process around these with the existing bugzilla workflow. Assign owners and track these to closure.
The same should be possible with other well known bug management tools as well.