I haven't used ledger, but it seems to be double entry accounting too. According to the example:

    2015/10/12 Exxon
        Expenses:Auto:Gas         $10.00
        Liabilities:MasterCard   $-10.00

whereas I would have something like:

    2015/10/12   Exxon  $10.00  MasterCard  ->  Gas 

The idea would be that the form of the transaction doesn't allow you to screw up - it is neccessarily balanced because you only give the amount once. A bit like a typed language only allows well-formed programs to run.