A 'Description' box is available on Calendar Events, Discussions, Tasks, Policies and Pages. This box is like a cut-down version of Microsoft WORD. See the example below.
There is virtually no limit to the amount of text etc that you can add and this can be formatted in lots of ways.
One useful function is the ability to add and format tables in the Description area.
The sub-menu links on the left give some examples about how to use these functions (especially the setting up and formatting of Tables).