A slicer is the software that makes 3d models printable. By choosing settings like material type and fill density, then processing your model, you give your model substance and produce instructions for your printer to make it real. These options determine how heavy the resulting object will be, how durable, and how costly.
Simplify3d runs on most operating systems and provides a stable environment with options to save all settings, slice models into multiple processes with different characteristics, and provides excellent support settings. There is also a handy gCode preview tool that can be very helpful, and a printer control interface. Simplify3d can be purchased through MakerGear when buying a printer and already has optimized settings available for MakerGear products and many others.
Slic3r is a free program developed by a community that has helped make the RepRap project enjoyable. Slic3r runs on a variety of operating systems, and has many features.
Suggested Slic3r settings for the MakerGear M2 are contained in this file: M2General129.ini
Slic3r is also included in the Pronterface printing suite.