Commit
One saved change to code, recorded with an author, a time, and a short message describing what changed.
What it tells you about a developer
Steady commits over months signal consistent output and durable habits. Clear, specific commit messages usually come from developers who communicate well everywhere else too.
The commit is the basic unit of developer work. A developer commits several times a day, and the full list is their commit history. It shows the rhythm of someone's output over years. Counts measure volume alone: one commit can hold a week of design work or a one-character fix.