Types of contracts
At launch, our beta on Arbitrum will offer several pairs (ETHDAI, ETHUSDC, DAIUSDC) with different maturities.
This will change in the future as we integrate more pairs and maturities, and eventually move to Ethereum too.
Please bear in mind that when opening a short position, under the hood Contango will open a long position through an inverse contract. The latter is simply a linear contract that offers the opposite pair (e.g. DAIETH). Indeed, going long on the inverse (e.g. DAIETH) is equivalent as going short on the linear contract (e.g. ETHDAI).
From a user's perspective, the only noticeable difference between longing and shorting an asset is the collateral being posted. When going short you should post the base currency (e.g. ETH) and not the quote (e.g. DAI).
This is useful for instance when you have ETH and want to hedge your position by shorting it with an expirable: you can go on Contango and post it directly as collateral in a non-custodial way.