Commit

A single set of changes.

What can it contain?

A single commit might contain addition and/or modification and/or removal of files.

How does it work?

Imagine a repository with two commits:

the first commit adds files a.txt and b.txt.
the second commit removes file a.txt, modifies b.txt and adds c.txt.

The repository now contains modified b.txt and c.txt. If you want, you can go back in time to the first commit - anytime. And without losing the ability to travel back to the last commit again.

Time travel is made possible thanks to the .git directory, which contains the history of changes in an efficient format.

How can I reference specific commit?

Each commit has so-called commit hash. It is unique across the repository.

Each commit has also a commit message, which is a brief summary of changes specified by you.

Commit messages are referenced in this book like: "Commit message"