Git is an open-source version control system known for its speed, stability, and distributed collaboration model. Originally created in 2006 to manage the entire Linux kernel, Git now boasts a comprehensive feature set, an active development team, and several free hosting communities.
Git was designed from the ground up, paying little attention to the existing standards of centralized versioning systems. So, if you're coming from an SVN or CVS background, try to forget everything you know about version control before reading this guide.
Distributed software development is fundamentally different from centralized version control systems. Instead of storing file information in a single central repository, Git gives every developer a full copy of the repository. To facilitate collaboration, Git lets each of these repositories share changes with any other repository.
Having a complete repository on your local machine has a far-reaching impact on the development cycle...
First, a local copy of the repository means that almost all version control actions are much faster. Instead of communicating with the central server over a network connection, Git actions are performed on the local machine. This also means you can work offline without changing your workflow.
Since each collaborator essentially has a backup of the whole project, the risk of a server crash, a corrupted repository, or any other type of data loss is much lower than that of centralized systems that rely on a single point-of-access.
Every copy of a Git repository, whether local or remote, retains the full history of a project. Having a complete, isolated development environment gives each user the freedom to experiment with new additions before polishing them up into clean, publishable commits.
A complete history for each developer also means a divergent history for each developer. As soon as you make a single local commit, you're out of sync with everyone else on the project. To cope with this massive amount of branching, Git became very good at merging divergent lines of development.