What is the use of Subledger Journal Entries in SLA ??

Hi First of all I was of the opinion that Subledger Accounting module is only used for doing setups etc i.e we can use the tools like AMB and TAB to setup accounting definitions and build transaction accounts etc but not enter transactions / journals etc.
However when I was going thru the SLA Imp Guide, then I saw a chapter which explains how to enter the Subledger Journal ,although the guide did not explain the functionality of that. And so I investigated and I found that the menu "Subledger Journal Entries" was  missing and when I added that menu I could create Subledger journal entries and adding supporting references etc.