difference between git repository and project

A Repository as documented on GitHub:

A repository is the most basic element of GitHub. 
They are 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.