How do Jehovah's Witnesses define "active" membership?

On several occations I have seen terms used for _active_ vs _inactive_ Jehovah's Witness church members. I have also seen inactive ones referred to as _passive_ or even with both monikers together as _inactive passive_. Based on other experiences with JW's, I imagine these terms have fairly specific definitions. I just don't know what they are. This makes me wonder exactly how membership is defined and what makes the difference between an active an a inactive member? What officially defines a person as one or the other, and what is the process and result of an official status change?