A commit records a group of changes in git with a message, an author, and a place in history. Saving a file only updates your local copy; a commit marks the moment you say “keep this set of changes as one meaningful step.” A good one groups related work under a message that explains the step, like “Fix search filter on mobile.”
Picture photographing a whiteboard before you keep working. The photo doesn’t stop you from changing things. It gives you a record of what the board looked like, so if the next idea goes badly, you can look back.
Why you care
When an agent edits a codebase, its changes stay loose until they’re committed. If a branch carries five commits, you can see the path the work took and inspect the one that went wrong; the log shows that trail of messages, authors, and dates. You don’t need to memorize Git commands, just the operating idea: make a meaningful change, record it clearly, and leave a trail someone else can inspect. Serious work needs a history, and commits are the history.