Individual cells function very much like the IPython command line, with the slight change that hitting Enter does not cause the cell to be executed, but instead creates a new line to be typed on. In order to execute a cell, there are many options:
Alt + Enter runs the current cell and inserts a new one below
Ctrl + Enter runs the current cell and does not create a new cell
The Cell menu item contains a list of ways to run cells, including Run All
The result of cell execution is very similar to what would be expected from the command line, for example:
Note that the bottom cell contains Markdown text (http://daringfireball.net/projects/markdown/) rather than Python code. Markdown is a plain text formatting syntax meant to be easily convertible to HTML. Why docstrings are in reStructuredText and notebook cells are in Markdown is a mystery. Luckily, they are fairly similar.
Fixing the error in cell 3 allows the code in the next cell to run, which highlights a neat feature: the...