Wolfram Language & System 10.0 (2014)|Legacy Documentation
A group of cells can be either open or closed. When it is open, you can see all the cells in it explicitly. But when it is closed, you see only the cell around which the group is closed. Cell groups are typically closed around the first or heading cell in the group, but you can close a group around any cell in that group.
Large notebooks are often distributed with many closed groups of cells, so that when you first look at the notebook, you see just an outline of its contents. You can then open parts you are interested in by double‐clicking the appropriate brackets.
Each cell within a notebook is assigned a particular style which indicates its role within the notebook. Thus, for example, material intended as input to be executed by the Wolfram Language kernel is typically in Input style, while text that is intended purely to be read is typically in Text style.
Ordinary Wolfram System notebooks can be read by non-Wolfram System users using the free product, Wolfram CDF Player, which allows viewing and printing, but does not allow computations of any kind to be performed. This product also supports computable document files (.cdf) and notebook player files (.nbp), which have been specially prepared by Wolfram Research to allow interaction with dynamic content from the output of Manipulate. For example, all the notebook content on The Wolfram Demonstrations Project site is available as notebook player files.
|Wolfram System front end||creating and editing Wolfram System notebooks|
|Wolfram Language kernel||doing computations in notebooks|
|Wolfram CDF Player||reading .cdf files and running Demonstrations|