Layer Jungle

[Crankey]

I have been watching a vid tutorial and it's about layers.

The video starts out with a picture and under the Layers menu there are several layers present.
Each of these layers can be manipulated in various ways, however there is no mention as to how these layers came to be.

Any photo I open has the image locked onto a background layer.
Do I need to create new layers and select the different components of the image and apply them to there respective layers. That could be a bit sloppy couldnt it.

Thanks for any help