To kick off collaboration, my teammate does some local work worthy of sharing--the commit represented by the pink circle.
Key Learning Points:
✅ git commit is a local-only operation. No communication happens to or from any remote repo.
✅ Because git commit is local-only, my teammate's main moves, but not origin/main.
✅ Because git commit is local-only, main on the remote called "origin" does not move either (at least, not as a result of this teammate's commit. Somebody else could have git push'd and hence moved main on the remote, but the teammate won't know about it yet).