As I run a pipeline, it showed me this point
How does this actually work? And is the the status update on existing source code commit or a new commit saved all the config of the running pipeline?
I tried to look at the MS docs but it wasn't clear for me.
No. A pipeline run doesn't create a new commit. A commit comes from the repository. So anytime you restart the same pipeline it will use the same commit id unless there is a change on the repository.