Slicer

A slicer is the software step between a 3D model file and an actual print. It takes a solid digital shape, cuts it into flat horizontal layers, and works out the exact path the nozzle needs to travel for every single layer, along with when to extrude, when to travel without extruding, and when to cool down or heat up.

Beyond just slicing shapes into layers, this software is where most of the settings that decide print quality actually live: layer height, print speed, infill density and pattern, support structures, retraction, and temperatures for both the nozzle and the bed. Two people printing the exact same model can get very different results depending entirely on slicer settings.

Most slicers include starting profiles for common printers and filaments, which is the sensible place for a beginner to start rather than manually setting every value from scratch. A common mistake is copying someone else's advanced settings from a different printer and filament combination and expecting identical results, when small hardware differences change what actually works.