The scenes made as PSD files are made for using 2D animation softwares which support these files. One of these softwares which can be connected to Photoshop is Cartoon animator 4 among many other 2D animation softwares.
All parts are separate and can be rearranged in the scene itself or can be used in other different scenes. The scene can be used in your projects and custom creations. Every object can be moved, modified, enlarged, decreased or it can be removed from the scene so you can adjust it to your needs.