In 3D modeling slicers, layers are horizontal cross-sections that slicer software divides a 3D model into—3D printers build objects by stacking these thin, flat slices one on top of another.
Layer height (the thickness of each slice) balances print quality and speed: thinner layers (e.g., 0.1mm) create smoother surfaces but take longer, while thicker layers (e.g., 0.3mm) print faster but with coarser details.
For beginners, start with a 0.2mm default layer height in tools like Cura or PrusaSlicer—it’s a safe middle ground to learn how layer settings affect your prints.