Eclipse Che allows developers to code in the cloud using Docker containers. It provides developer workspaces that contain runtime environments defined by Dockerfiles. Projects are mounted into these runtimes so developers can run commands like 'mvn' and 'start mysql'. The demo shows how to create custom workspaces that define their own commands and runtimes. Eclipse Che uses Docker to provide developer workspaces with custom commands and runtimes in a portable way without complexity.