What it means
A costs order is a court order deciding which party must pay legal costs and to what extent. In Australian civil litigation, costs usually "follow the event", meaning the unsuccessful party is ordered to pay a portion of the successful party's costs, commonly on a party-party basis. Costs are within the court's discretion and can be affected by conduct and settlement offers. Note that small claims tribunals often limit or exclude costs awards.
How it's used
Having won the case, the plaintiff also obtained a costs order requiring the defendant to pay her legal expenses.