I would say that it is the codifying of the details of the nature and extent of the entries. 

The subtypes of said nature, e.g. the type would be 1.0.. or 2.0... (credit and debt), then the subsequent numbers would classify the transactions under that nature.

To make an accurate distinction and establish differences it would take someone into accounting, and here we deal with more basic English learners. Anyway, let´s wait for someone into accounting to help you out further.