Deployment Manager follows the industry best practices DevOps, specifically the principle of Build Once, Deploy Many. In terms of Pega applications, there isn’t an explicit build step, however the application packaging process using the Product rule is the equivalent of the build step for code based projects. The product archive (package) is generated only on the dev environment, and then published to the Devrepository. Higher environments such as Quality Assurance and Staging will pick the same package from Development repository.
If the Production ready option is selected, then once all tasks are successfully completed, the same package is promoted (copied over) to the Prodrepository and from there it’s deployed on Production environment. This will ensure that only fully validated application product archives are available to be deployed to production.