GitHub recently introduced a new feature called Projects. This provides a visual board that is typical of many Project Management tools:
A Repository as documented on GitHub:
A repository is the most basic element of GitHub. They're easiest to imagine as a project's folder. A repository contains all of the project files (including documentation), and stores each file's revision history. Repositories can have multiple collaborators and can be either public or private.
A Project as documented on GitHub:
Project boards on GitHub help you organize and prioritize your work. You can create project boards for specific feature work, comprehensive roadmaps, or even release checklists. With project boards, you have the flexibility to create customized workflows that suit your needs.
Part of the confusion is that the new feature, Projects, conflicts with the overloaded usage of the term project in the documentation above.