Working with layers
Why work in layers?
Working in layers is the most efficient way to organize our work. The best way to explain it is probably with a map. Imagine that you want to create a cartography and that you have all the graphic elements (contour lines, rivers, roads, towns, vegetation ...) in a single layer. Every time you went to pick up or view one of them you would have to select all of its components. On the other hand, if you work by layers you can select them separately, hide them, move the layer up or down, etc.
You should imagine the layers as sheets of clear plastic that allow you to see what's underneath, even if they belong to another lower layer. It can be operated through the top menu "Layers", through the bottom status bar or through the "Layers" dialog.
By clicking on the eye you can show or hide the layer and by clicking on the padlock you can lock or unlock it.