EthUSD is an Ether backed stablecoin pegged to the USD.

Users can receive EthUSD by paying Ether into the contract.

At a later date they can withdraw Ether.

If the price of Ether doubles and they withdraw they'll receive half as much Ether as they deposited (The same amount in USD). The remaining ether is stored in the contract to cover losses if the price falls.

If the price of Ether falls the user who bought in 2 Ether, and the price halved, they'd get back 4 Ethers.

EthUSD is simpler than other stablecoins because it doesn't try to solve the bad collateral problem. If the price of the collateral (Ether) starts to fall the stablecoin will fall in value at at the same rate of depreciation.

This token is minted on demand as ether is paid into it.