To understand more about Jarvis it is helpful to review a little of how the FX market works. With FX either the  broker or the prime broker has an account with a liquidity provider, which provides the Forex liquidity. When you deposit money into the broker account, the most brokers will take some  funds and  put them in a centralized USD pool, and the broker will open a mirrored trading account in USD in your trading platform (let say, it is MT4). So the money you see in MT4 is the mirror of the money you have deposited in the banking account of the broker. When you take a trade, you make a loan within the liquidity of the broker. You trade with their money, and a leverage.

So Jarvis does the same : we open an account within a Forex Liquidity provider (not a broker). As example, 1 million USD deposit. But instead of depositing money in a banking account, you deposit it in your wallet.

From your wallet, either you have fiat (let say 10 000 USD) or you have another asset (let's assume few Bitcoins). When you trade FX, we will lock your money (either the 10k USD or the BTC you have) into an escrow. Then, a loan is triggered in the liquidity pool connected to the Forex liquidity provider. You can now trade Fx without a broker, directly from your wallet.

I hope it answers your question

There is a drawing on the whitepaper, by the way, to explain a bit how things are structured.