In defect life cycle when a defect is found it is given a status :New.
Then it is passed to the development project manager to check whether it is a valid defect or not.If the defect is not valid status is given Rejected . But if it is a valid defect then manager check whether it is in scope or not. If it is not in scope then status given becomes Deffered. Likewise different status comes up further.
For example: Suppose we found some valid defect(say functional) in our email but that is not the part of our current release( or we can say that this functionality is not required at this time so lets delay it and do other important task.)so deffered it.
The bug, changed to deferred state means the bug is
expected to be fixed in next releases. The reasons for
changing the bug to this state have many factors. Some of
them are priority of the bug may be low, lack of time for
the release or the bug may not have major effect on the
Valid issue But due to time consuming or if the severity is trivial, and if it is future functionality or if it is not a blocker then that bug will be suspended or acknowledged by developer, I.E it is yet to be fixed in the next Build.
After a defect opened, it's may be assigned or deferred.
Deferred status is due lack of information about the defect.After gathering new information it will reopen.But if information is sufficient after opened status the status will be assigned.