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:
Selects the extruder to be used for printing your Skirt
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.
How far away your skirt will be from your part.
# of perimeter outlines for your skirt.
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.
Selects the extruder to be used for printing your Raft
How many layers your raft will be.
How far away your part the raft will extend out to.
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.