To use the Yocto Project, you need a release of the Yocto Project locally installed on your development system. The locally installed set of files is referred to as the Source Directory in the Yocto Project documentation.
You create your Source Directory by using
Git to clone a local
copy of the upstream poky
repository.
Working from a copy of the upstream repository allows you to contribute back into the Yocto Project or simply work with the latest software on a development branch. Because Git maintains and creates an upstream repository with a complete history of changes and you are working with a local clone of that repository, you have access to all the Yocto Project development branches and tag names used in the upstream repository.