In SketchUp 2021, the most "interesting" aspect of layers is that they technically don't exist anymore—they were officially renamed to starting with the 2020 version to better reflect their function as a visibility tool rather than a structural one. Key Developments in SketchUp 2021 Visibility
In AutoCAD or Photoshop, "Layers" control geometry AND stacking order. In SketchUp 2021 , Layers (Tags) do not control visibility priority. They control visibility sets . Remember: Geometry lives on one Layer, but Groups/Components have their own Layer. layers sketchup 2021