The 'fatal: not a git repository' error occurs when Git commands are executed in a directory that doesn’t contain a Git repository. Each Git project is marked by a hidden `.git` folder that stores the project's version history and configurations. To resolve this error, first verify that you are in the correct directory by running `pwd` (on Unix-like systems) or `cd` (on Windows). If your project lacks a `.git` folder, you can initialize a new Git repository by running `git init` in the project directory. Alternatively, if you accidentally deleted the `.git` folder, restore it if possible, as this folder is crucial to Git operations. Sometimes, switching to the project’s root folder resolves the error when working in nested directories. If your intent was to clone a repository instead, make sure to clone it from GitHub using `git clone `, which will include the required `.git` folder for a functional Git repository.