The Yocto Project is a Linux Foundation workgroup defined as:
The Yocto Project is an open source collaboration project that provides templates, tools, and methods to help us create custom Linux-based systems for embedded products regardless of the hardware architecture. Being managed by a Linux Foundation fellow, the project remains independent of its member organizations that participate in various ways and provide resources to the project.
It was founded in 2010 as a collaboration of many hardware manufacturers, open source operating systems, vendors, and electronics companies in an effort to reduce their work duplication, provide resources and information catering to both new and experienced users.
Among these resources is OpenEmbedded-Core, the core system component, provided by the OpenEmbedded project.
The Yocto Project is, therefore, a community open source project that aggregates several companies, communities, projects, and tools, gathering people with the same purpose to build Linux-based embedded products; all these components are in the same boat, being driven by its community needs to work together.