The Class Break Style allows you to define how area, line, or point based features will be rendered on the map based upon a range of values in your layer's attribute data. Each class break definition will create a new area, line, or point style and assign them to your features based on the value of their attribute data. This style gives you a thematic representation of data that has a range of values. The 2011 GDP Per Capita sample map is a good example of how a class break style might be used to represent data on a map.
Name - The name of the class break style. Choosing a descriptive name can help you quickly identify styles when you are compositing many of them together.
Column Name - Sets the column data the class break style will use to determine which style each feature will use based on that feature's column value.
Class breaks creates an area, line, or point style and assigns a feature to it based on the starting value in the class break. So if you had two class breaks, one with a starting value of zero and another with a starting value of 10, and a feature who's column value was five, the class break style would assign it to the first class break. If the feature's value was 11, it would be assigned to the class break with the starting value of 10. There are two ways to create class breaks:
Add New - Creates a new class break with an area, line, or point style and a starting value of zero, which can be altered to the desired amount. Any values in the column is greater than or equal to the value of the class break will be assigned the associated area, line, or point style.
Auto Generate - Opens a windows for you to set parameters quickly for your class breaks rather than going through them individually. In this window, you can set a number to be divided evenly within your data's range. You can then set the lowest and highest value for the data and also set the starting and ending colors that you want to use. These two colors are then interpolated to give a nice transition between them. Once generated, there will be a number of class breaks equal to the amount you divided the data. The column data that falls in between two class breaks will be assigned the associated area, line, or point style.
Each class break created has either an area, line, or point style attached to it. These can be modified the same way as if you had created one using the add style button. You can modify a style by selecting it from the Styles List.