Slicing describes the process of using specified parameters (recipes) to generate gcode to physically produce your model(s), layer by layer.
For other 3D Printers, this gcode tells the printer how much material to dispense on each printing move - this is the "E" value. However, since we generate flow commands on the fly for each printing move (as well as advance/retract for transitioning between printing and non-printing moves), we don't use this E value - please see the Flow_Rate page for more detail on this.
We support the Slic3r program, which uses three recipes: Print, Printer, and Filament (or Extruder). Since we do not use these E values, our main purpose for using these recipes is as follows:
We use the Print recipe to configure the physical characteristics of the print - where to put material (and by inference, where not to put material). This includes specifying your path width (normally 110% of your nozzle diameter), your layer thickness (normally 25-75% of your nozzle diameter), your number of solid perimeters (top, bottom, and vertical), your infill pattern and density, support material (if desired), and printing speed.
We use the Filament recipe to configure heating and/or cooling of the print head(s) and the bed.
We use the Printer recipe to specify actions before and after tool changes, and before layer changes.