Jupyter is an offshoot of the IPython project, which aims to create a better interactive mode for Python. While Jupyter incorporates IPython, it's still available as a standalone program.

Any Python module that runs well in a notebook interface (essentially, anything that writes to stdout as part of its behavior) is a good candidate for this. Sharing code and data generally.

Because of the client/server architecture, it is very simple to share notebooks with other users. You can — in theory — use Jupyter for anything you could use Python for.