It's a nice, fluent way of saying "Run this jobs sequentially, one after the previous one is complete.".
If you have a task which takes some steps to be completed, you can track the job chain used to do that and know the
status for each job.
If you are releasing a new podcast, for example, and it has to be optimized, compressed and released, you can track
this steps by adding a steps relationship to your Podcast model: