$ man commits

Commits

A snapshot of your files at a specific point in time with a message explaining what changed.

by Shawn Tenam

Commits are your paper trail. They tell the story of how you built something. Good commit messages make debugging easier. Bad commit messages make you hate yourself when you're trying to figure out what broke.

git commit -m "add user authentication". The message should say what you did and why. Not "fix stuff" or "updates". That's useless.