As an Australian Resident, the first $18,200 of your income is tax-free. Therefore, if your total income is less than $18,200 you won't pay any tax, and if your employee withholds any tax on this amount, you will be refunded it!
An important note is that when you commence your employment you will complete your Tax File Number Declaration form. On this form, you will need to tick the box that notifies your employer that you want to claim the tax free threshold.
People with two jobs need to be careful not to tick the box for both employers, as this could mean that neither employer withholds tax as they assume you are only working for them and may not earn the $18,200. In this case, you should only tick the box when completing the form for one of the employers.