These settings very much relate to the strength of the print, as they define the internal structure of the print.
The most important setting here is the fill density, which defines the amount of plastic inside the print. A higher fill density means that there’s more plastic on the inside of your print, leading to a stronger object. In general, a fill density between 10% and 20% will be strong enough for most objects, but you can increase it if necessary. You can also decide to print the object completely hollow, which is desired in some cases. This can be done by simply setting the fill density to 0%.
This option is available since Cura version 15.06 and is an interesting feature if the quality and looks of the infill are less important. It allows you to print the infill at a different layer height than the rest of the print. This means that you can use thicker layers for the infill, leading to a shorter overall print time. When using this option, you have to take into account that the infill thickness always has to be a multiple of the layer height. You could for example choose to use an infill thickness of 0.2 mm if the general layer height is set to 0.1 mm.