Current DYDX holders have their tokens on Ethereum. As dYdX transitions into being launched as a Cosmos SDK chain, the original DYDX token holders will only be able to access the benefits of the Cosmos SDK chain (staking, governance etc.) after they move their tokens from Ethereum to dYdX chain. To move these tokens dYdX has provided with a bridge contract that makes it easy for anyone to send their tokens from Ethereum to dYdX chain.