GitDiagram is an online tool that converts any GitHub repository into an interactive chart, enabling users to quickly understand and visualize project structures. This tool is crucial for developers and project managers as it helps them gain insights into the organization of codebases and their dependencies. GitDiagram was created by developer Ahmed Khaleel and can be accessed via API and GitHub. Currently, the tool is free to use, and users can utilize it by replacing 'hub' with 'diagram' in the GitHub URL.