Descriptions to describe your transactions are only compulsory in a few circumstances.
A description pop up will appear for you to complete.
As a general rule, the use of the DESCRIPTION FIELD should be kept to a minimum and should only be used where the expense you have paid cannot be adequately understood by the name of the business you are paying and the Column Header you are placing it under.
For Instance:
A description would be required for AMP Insurance $1,237
That notation doesn't describe the type of Insurance, so a description of "Life insurance" would identify the nature of the payment.
Something like BP Fuel $87, would not require a description, as clearly you can see what it is.
Why Bother with Descriptiona at all?
The chances are your accountant or tax return will require information about the payment. So better off doing it now than digging it up later.