Many employers offer salary packaging to attract and retain employees with additional benefits. If it's done well it can be good for both the employer and the employee. The employer benefits from being able to attract top quality candidates; the employee benefits from a lower tax liability.
In a nutshell, salary packaging is where an employer offers their staff the opportunity to pay for certain goods and services out of pre-tax income. These goods and services can include such things as computers, cars, health insurance, childcare and superannuation contributions (commonly known as salary sacrificing).
By paying for these goods and services before tax, it reduces your gross salary so that your tax liability is lower. As a result, it is more likely to be tax effective if you are in a higher tax bracket.