A cash account allows you to participate in both Drops ("Primary") and Trading ("Secondary) with a pre-funded account.
You will not be able to participate in Trading without cash in your cash account. (You can still participate in Drops without a cash account — we will transfer funds from your linked Bank Account instead.)
Generally, we recommend transferring funds into your cash account at least 3-5 business days before you plan to use them in order to allow your funds to settle.