A teensy excerpt from the awesome Excel book I mentioned earlier

[Greg]

Elliot Bendoly wrote:
Cells in spreadsheets can contain:

• Fixed data: Data you’ve entered, numerical or otherwise.
  
• Formatting: Background color, border thickness, font type, and so on.
  
• Labels: References other than the standard ColumnRow reference.
  
• Comments: Notes regarding the contents.
  
• Formulae: Can be mathematical/statistical, text based, or a range of other types
  such as logic based or search oriented.
  
• Live data links: Data that are drawn from an externally linked source, such as a
  database or the Internet.
  

-- from Excel Basics to Blackbelt, by Elliot Bendoly. Page 8 (!!)

Unlike the normal approaches to teaching Excel, which invariably involves chapters on putting things into cells and making them look pretty, this author begins with a overview of how cells can be used to store or reflect information.

ISBN: 9780521889056