When you create or import an image in Paint Shop Pro, the image has a single layer. Depending on the type of image you created or imported, you'll see in the Layers palette that the single layer may be labeled Background (this is the case when opening images such as photos or screen captures), Raster, Vector, or Art Media.
For most simple image retouches and corrections, you do not have to
add any layers. However, it's generally a good habit to simply duplicate
the layer (by clicking the Duplicate
Layer button 
in the Layers palette toolbar) before
applying actions such as the photo correction commands. By applying any
changes to the duplicated layer, you'll always preserve the original image
on its own layer. And when you intend to do more complex work such as
add elements to the image, create photo compostions, add text and other
effects, etc., it's highly encouraged that you utilize layers for these
tasks.
Each layer that you add begins as a transparent sheet over the background. As you add brush strokes, vector objects, or text, you cover up parts of the Background layer. Transparent parts allow you to see through to underlying layers. You can stack up multiple layers to create whatever effect you’d like—such as artistic compositions, photo collages, or complex illustrations. For more information about using layers, see: Types of Layers
Ways to use layers: