To make a commit we'll use the git commit -m "your_commitmessage" command.
Instead, prefer using git commit -v if you are not using git commit -p (perhaps also with -v) to force a pause to think about the story you want to write from the view of your git log. Using git commit -m encourages less thoughtful history being written.
Use the editor coming up, and the diff presented to remind you why the changes are committed in this commit, in this one snapshot.