Category attributes allow the store owner to define specific attributes that all products in that category will have. Once the attribute is added here, it will appear on the attributes tab of the product edit screen.
Attributes can be used for product features, specifications, etc. The above example shows an example of how attributes could be used in a store that sells motors.
When the customer is shopping in this category, they will see a shop by nav on the left side with the attributes you add here as headings. For this example the shop by nav would say:
Under each of these headings would be all the options you designated for each product. So on one product in this category you may designate the horsepower as 10HP and this would be an option to click on under the "Shop By HP" heading.