MECE stands for Mutually Exclusive, Collectively Exhaustive and serves as an organizing framework used by management consulting firms, such as McKinsey and BCG as a way to organize reports and complicated data.  Due to its effectiveness, it has made it's way into the larger business community.  An example MECE arrangement would be departments within an organization, year hired for employees, the choice to eat in or eat out.  MECE can be used to simplify complex ideas.