The title of "pastor" I can understand

Because it describes the vocation. It's like calling people "superintendent" or "Principal" or "teacher" or "teacher's assistant." That's the role they play in the organization.

Titles like "Bishop" ......... Cardinal or Pope are a bit more vague to me and seem to denote distinction more than job description.

A title like "Reverend" has me quite baffled though. How does one BECOME a Reverend and what distinguishes a Reverend from other people?

-Vince