You will notice that 3D prints sometimes show small strands of plastic where the 3D printer did not print, but was moving from one place to another. These strands are also regarded as stringing. There are certain measures you can take to deal with stringing.
Retraction is the mechanic that pulls the filament back a little bit, in order to prevent the filament from leaking from the nozzle during the traveling of the print head. By turning retraction on in Simplify3D, the amount of stringing is already significantly reduced.
Reducing the temperature at which you print can also reduce the stringing. A higher temperature means that the material you are printing with will turn more liquid, which causes it to more easily drip from the nozzle. Setting your 3D printer at a lower temperature can cause the material to string less, as it is less liquid. This temperature, of course, depends on the material you are using. You will find more on this subject on the materials page.
With a lower temperature, your materials can start under-extruding as you are still printing at the same speed. In this case, lowering the 3D printing speed can be beneficial to reduce stringing.
When printing at a high temperature, the opposite can work. The material has less time to drip from the nozzle when increasing the travel speed. Important to note is that you should increase the travel speed, not the printing speed. Increasing the print speed impacts the quality of your prints.