Apple Pages '09 - Manual (Page 223)

Chapter 10 Creating Charts from Data 223
If you plot this data as a column chart, it shows four sets of two bars, spanning four
years.
The chart legend denotes
the four data series.
Each data set contains four bars,
one from each data series.
These two bars of the
same color represent one
data series.
Each bar represents
one data point.
In this chart, Region 1 and Region 2 are called the data series because the data
points (numbers of birds) from each region are represented by a series of columns
of the same color, one for each year. Each column for Region 1 is set beside the
corresponding column for Region 2, and each side-by-side set of columns is called a
data set or category (2007 is a category, 2008 is a category, and so on).