The Three States of Git
Git operates locally across three primary areas: the Working Directory, the Staging Area (Index), and the Git Repository.
The Working Directory is a single checkout of one version of the project. Files here can be modified, untracked, or deleted.
The Staging Area is a file that stores information about what will go into your next commit. You use "git add" to move changes here.
Commits and Cryptography
A commit takes a snapshot of the staging area and permanently stores it in the Git repository. Every commit is cryptographically hashed (SHA-1) to ensure data integrity.
Because every commit points to its parent, Git forms a Directed Acyclic Graph (DAG) of project history.