It's a Macquarie Bank account in your name. The account is a cash management account (CMA) provided by Macquarie, which is free to set up, earns interest and makes moving money into USD cheaper and easier.
You can use POLi to fund your US account (this is faster) or you can fund your AUD wallet and then transfer your AUD into USD on Stake. You need to the AUD wallet to bring your funds back from the US and then deposit them into your local bank account.
As Macquarie takes 1-2 days to verify your details, you may have to wait until they have completed this before transferring your $ from your AUD wallet to your US trading account.
For verified accounts, POLi remains the fastest way to fund.