What's the difference between a contributor and reviewer?

Answer:

The two most noteworthy differences between a Contributor and a Reviewer are as follows: 

1. Contributors can ADD content items, while a Reviewer CANNOT.
2. Contributors can EDIT most fields in the DivvyHQ content editor, while a Reviewer has a READ-ONLY view. 

When working with content items within the content editor, Reviewers can still mark content as "Approved", add comments, manage their tasks and upload/download files, but that's it. Most other fields are locked down.