Apple Numbers '08 - Manual (Page 19)

Chapter 1 Numbers Tools and Techniques 19
Pick the template that best fits your purpose. If you want to start from a plain
spreadsheet, without preformatting, pick the Blank template. After selecting a
template, click Choose to work with a new spreadsheet based on the selected
template.
Templates contain predefined sheets, tables, and other elements that help you get
started.
Sheets let you divide information into groups of related objects. You might use one
sheet for data from 2006 and another sheet for data from 2007.
Predefined tables usually contain text, formulas, and sample data. You can replace data
in the predefined tables with your own data, and you can add columns and rows or
reformat the tables. You can also add sheets and other objects, such as charts, images,
and text.
Explanatory comments are included in some of the templates.