Skirt Settings
Skirts are really useful for priming your extruder prior to printing. I generally print with a skirt offset of 4 mm and 2 outlines. However, changing the offset to 0 mm, offers the ability to create a "brim" that will connect to your part and help create surface adhesion. For more information on skirts, brims, rafts, this tutorial is very helpful:
http://www.simplify3d.com/support/tutorials/rafts-skirts-and-brims/
Skirt Extruder: Selects the extruder to be used for printing your Skirt
Skirt Layers: How tall your skirt will be. If you want the skirt to be as tall as your part, you can just place 99999 in this field.
Skirt Offset:How far away your skirt will be from your part.
Skirt Outlines: # of perimeter outlines for your skirt.
Raft Settings
A raft offers a base understructure that will contour to the outline of your print, increasing the surface area to the bed. This in-turn will offer more adhesion to the print bed. However, because rafts take a long time to print and use a lot of material, it is only recommended to use rafts for prints that have a low surface area with the print bed or that generally don’t have a good base will often benefit from a raft. Also, whether due to the design of the printer or calibration, those users with beds that are slightly uneven have often found that rafts can provide a good foundation.
Raft Extruder: Selects the extruder to be used for printing your Raft
Raft Layers: How many layers your raft will be.
Raft Offset:How far away your part the raft will extend out to.
Separation: How much extra distance on the Z-axis from the raft to to the bottom of your part.
Raft Infill %: This will typically be set around 80%, set the top layer of your rafts infill. For rafts made from dissolvable filament, upping this to 100% may be helpful.
Disable Base Layers: Disables the thicker layers at the start of the raft, disabling this can be helpful if your rafts stick to the bed too much.