This derived property is very useful when you want to split large amounts of numerical values into groups. For example, lengths or prices:

Normally (length in cm)	Grouped
6	1 to 10 cm
8
9
10	10 to 20 cm
14
17
19
21	20 to 30 cm
23
28

If you want to group numeric values such as price, you need to save the value as a property instead of a characteristic. Is your price still just a characteristic, read this article first: 'How come I can't select a price or product title in a derived property?'. Once you've done this, you can start grouping prices. To do this, navigate to Catalog > Derived properties. Then click New. Now choose the type Group, as in the example below.
You'll land on the screen below. Give the derived property a name by filling in the Property name field. Select the property price under Property of the range values. Next, fill in the From and To values. In the right-hand column, Text, you'll type the values that should be shown in your webshop for that filter value. Click Save when you're done filling everything in. You'll stay on this screen. Now click the Preview tab to see what the derived values are for all your products.

Tip:
The screen where you can set up the grouping will only display 4 lines at first. When you save the settings after filling in those four lines, more lines will be added automatically.

NOTE: The range has a from - to value. Not a from - up to and including value.