Define the concept of mediator and moderator

In the research scenario below, define the mediator and moderator. Include evidence to support the definitions of the mediator and moderator for the research situation.

Scenario:

High satisfaction with one's direct supervisor leads to lower levels of employee turnover. In other words, employees who are highly satisfied with their direct supervisor are less likely to leave an organization than employees who are dissatisfied with their direct supervisor (DeConinck, 2009).