The goal of Cosmos is to achieve scalability in decentralized finance through a network of communicating blockchains. Cosmos will consist of an ecosystem of blockchain Hubs, each of which will have several Zones (sidechains) pegged to it. The main chain is called the Cosmos Hub. Creating a Zone is permissionless, but creating a new Hub will most likely require majority agreement.
The Cosmos Hub is designed to run Proof of Stake-based consensus and to keep track of the account balances in Cosmos Zones. Zones have to be able to submit a light client proof of their state to Hubs that the Hub can understand. Thus, Zones can run any consensus protocol that allows them to generate such proofs. Furthermore, while incentive mechanisms are deployed on the Hub level, Zones are responsible for providing enough incentive mechanisms to keep an honest majority.
The native token for Hubs is called Atoms. However, they are intended to be highly illiquid; thus, Cosmos does not have a native medium of exchange. To transfer value between Hubs will require proof of state transition. The transfer of tokens may need to pass through several Hubs from the origin to the destination zone.
To provide a medium of exchange, Cosmos is working on several initiatives, one of which is to image the Ethereum account state on to the Cosmos Hub. The Ether represented in that state can then flow into the Cosmos Hub. Note that this is an experiment.