Normals in 3D modeling are directional vectors attached to vertices or faces that indicate a surface’s orientation (which way it’s pointing).
They’re critical for realistic lighting and shading—software uses normals to calculate how light interacts with the model, so flipped normals can make a face look dark or invisible.
Most 3D tools let you view normals as small lines (e.g., Blender’s “Draw Normals” option) to fix issues quickly if surfaces don’t look right.