The purpose behind the use of layers is to add extra metadata to BitBake's database, or change it.

The most commonly added features are project related, such as applications, libraries, or a service server.

On the other hand, instead of adding new features, it is much more common to accommodate existing feature configurations to our needs, for example, the initial network values for a SSH server, or the custom boot splash image.

It means that we can include several types of metadata files on a new layer— recipes, images, and bbappend files—to change existing features. The script used to create the new layer can also create two example files: the first one, example_0.1.bb, is a recipe example; the second one, example_0.1.bbappend, is a bbappend example used to modify the feature included in example_0.1.bb. There are several other examples of bbappend files on meta-yocto-bsp and meta-yocto, and we explore some of their common uses in the next chapter.