A named sub-tree of revisions within a repository. Every non-empty repository includes at least one branch (usually main or master). Changes to content in one branch do not directly affect content in other branches, unless/until those branches are merged.
Commit
A timestamped record of a set of changes (new files, deleted files, modified files) made to a repository.
Fork
A remote copy of a remote repository—usually from one GitHub (or BitBucket, GitLab, etc.) account to another account—which shares the same history of commits (as of the moment the fork is created), and from which changes may be merged back into the original repository.
Git
A distributed version control system (DVCS), originally developed to help manage the source code of the Linux kernel.
GitHub
A service that hosts repositories online, easing propagation of changes between collaborators and providing a web-based interface for repository management and making simple content changes.
Markdown
A lightweight markup language with a plain-text-based syntax for formatting content. In most cases, Markdown is converted into HTML on the server side, before being sent to a browser for display.
Merge
The act of incorporating new changes (commits) from one clone of a repository into another clone of the same repository, one branch of a repository into another branch of the same repository, or one forked repository (or the source of the fork) into another fork of the same repository (or the source of the fork).
Repository
A collection of files (source code, documents, etc.), in which you create and manage content, typically related to a single project.
Version control system (VCS)
A system that records changes to a file or set of files over time so that you can recall specific versions.