What Does Manager mean in Group?

[netco]

It's mentioned in the user guide -> "Add Document".

Assign Reviewers: Assign system users or groups to review a document and comment on it. They may either reject or accept the review document. If you are in a group with a manager, that manager is automatically a reviewer of the document.

Assign Approvers: Assign system users or groups to approve a document and comment on it. They may either reject or approve the document. If you are in a group with a manager, that manager is automatically a approver of the document.

But, I didn't get it to work like proposed.