Git is a version control system that allows multiple people to work on the same codebase simultaneously without overwriting each other's work. It uses branches to isolate changes, commits to save snapshots of changes, and merges to combine changes from different branches. Github is a popular hosting service for Git repositories that provides additional collaboration features like pull requests and issue tracking. For Salesforce developers, using Git and Github can help track changes across sandboxes and orgs and allow for code reviews through pull requests. The new Salesforce DX toolset further integrates Salesforce development with Git by enabling automated deployments from GitHub repositories.