A Git repo is a (potentially very long) list of commits, where each commit represents the full state of the repository at a given point in time.

The git log command shows a history of the commits in a repository. This is what makes Git a version control system. You can see:

• Who made a commit
• When the commit was made
• What was changed

Each commit has a unique identifier called a “commit hash”. This is a long string of characters that uniquely identifies the commit: 5ba786fcc93e8092831c01e71444b9baa2228a4f

For convenience, you can refer to any commit or change within Git by using the first 7 characters of its hash: 5ba786f.

While commit hashes are derived from their content changes, there’s also some other stuff that affects the end hash. For example:

• The commit message
• The author’s name and email
• The date and time
• Parent (previous) commit hashes

Each commit points to its previous commit, so that is’s always possible to reconstruct the whole commit history of a single commit.

References

Next -> git-basic-plumbing