The Yocto Project is made up of a number of different internal projects that interoperate to provide a solid developer experience. One internal project, Poky, is a reference system that composes all of these internal projects together and provides a single base to test interoperability. When you download a comprehensive version of the Yocto Project, you are actually downloading Poky - inside, all of the components work together. Think of it as a base from which to start customizing your own Linux distribution.
To download the latest Yocto Project release, see the release notes for Poky 9.0.2 "Dylan".