3D printers work by adding tiny layers of plastic on top of each other. When we set this value higher, the printer has to add fewer layers and finishes the print more quickly. This is at the cost of minute details.
Generally, we would set the value lower only for small prints where the clarity of the details are important.
Default setting: 0.2mm
Infill is simply the repetitive structure used to take up space inside a print. Higher values make the print sturdier but use more plastic filament (i.e. are more expensive).
Generally, we would set the value higher only for prints that are designed to be load-bearing pieces.
Default setting: 25% infill