Poky contains a great amount of metadata spread over machine definition files, classes, and recipes. This metadata covers everything from simple applications to full graphical stacks and frameworks. BitBake has the ability to load metadata from multiple places, and those multiple metadata sets are known as metadata layers.

The biggest strength of using layers is the ability to split the metadata into logical units, which enables users to pick only the metadata set needed for the project. Using metadata layers improves the reuse of code and the ability to share work across different teams, communities, and vendors, increasing the code quality of the Yocto Project community as multiple entities are working together on the same metadata.

We may want to configure the system for different reasons, such as the need to enable/disable a feature or change build flags to enable architecture-specific optimizations. These are examples of customizations that can be done...