Ethereum is an open-source blockchain platform for transacting anything at all and not just bitcoin or any cryptocurrency.
Instead of bitcoin Ethereum uses a programmable unit referred to as smart contracts. These smart contracts are similar to real-world contracts only that they are not governed by any courts but by the blockchain network itself.
Whereas chain dot com provides a Chain Core - an enterprise-grade distributed system that powers secure, scalable, and highly available blockchain networks.
It follows the open-chain protocol which is built in collaboration with multiple financial companies