The IPython Notebook is a web-based interactive computational environment where you can combine code execution, text, mathematics, plots and rich media into a single document:

The IPython notebook with embedded text, code, math and figures.

These notebooks are normal files that can be shared with colleagues, converted to other formats such as HTML or PDF, etc. You can share any publicly available notebook by using theĀ IPython Notebook Viewer service which will render it as a static web page. This makes it easy to give your colleagues a document they can read immediately without having to install anything. iPython Notebook has evolved into Jupyter Notebook, which has support for over 40 programming languages, including Python, R, Julia and Scala.