Crunchy is a Python system that "formats and delivers html-written Python tutorials inside a browser window, adding interactive elements and snazzy navigation." The name, crunchy, is a
Monty Python reference.
Once you have downloaded and installed crunchy on your local computer, you can view HTML pages that have special crunchy-tags that will interact with crunchy and Python. One of the most useful features is that you can embed a Python interpreter window in your HTML presentation. If you are using this as an instructor, you can immediately demonstrate Python concepts from your browser. If you are a student, you can do this and then explore variations on your own.
Security is one potential issue with crunchy. Since an HTML file can invoke python from the browser, you need to trust its source. The authors have clearly thought about this and put in place various mechanisms to help. But, AFAIK, Python does not have a "sandbox" mechanism like Java's, so some risk remains.
If we want to use crunchy for teaching and have students install crunchy on their own computers, we'll have to look carefully at the security issues to ensure we understand and minimize the risk.
If you want to learn more about crunchy, the best way is to install it and view the crunchy tutorial that comes with it.