The insert designation is using the ANSI (American) system. Inserts sold here use the ISO system.
There is a very useful chart here that has both languages on it:
http://www.carbidedepot.com/formulas-insert-d.htm
With inserts, the importance of the information conveyed decreases considerably the further to the right that you read. Some of what is shown on your cutter is likely a manufacturer-specific grade of carbide.
For buying replacements, start at the left and get the basic shape. Then, for your chosen manufacturer, look at their literature and choose one of their offerings to suit the material being cut.