If Composer is used to assist with building aspects of a Fabric-based blockchain, then Cello is a tool to assist with the deployment of that blockchain to various servers and cloud services. Cello can be used to manage the blockchain infrastructure or launch new blockchains in a blockchain-as-a-service approach. Common lifecycle and deployment tasks include starting, stopping, and deleting a blockchain, deploying new nodes to an existing blockchain, and abstracting the blockchain operation so that it can run on local machines, in the cloud, in a virtual machine, and so on. Cello also allows monitoring and analytics.
Cello is primarily a tool for what is called DevOps, or the connection between development teams and production operations. It is primarily aimed at the Hyperledger Fabric project, but support for Sawtooth and Iroha is intended for future development.