What is the purpose of the Expense type on an Accounting Entry Template?

On the ADD and ADJ Accounting Entry Templates, there are fields for Contra Asset, Depr Expense, and Expense.  The first two are pretty self-explanatory, but what or where is the Expense value used?  We're a Fund Accounting shop, so we only use AM for straight-line depreciation.  No Tax methods or multi-currency. 

I have tried a plethora of test scenarios, but have not been able to create any accounting entries using the account entered in the Expense field, so I'm a bit confused as to what value I should put in there.

I would appreciate any clarification you can provide,

Andy