Deployments
Each push to your default branch produces a new deployment.
Each push to your default branch produces a new deployment.
Every push to your repo triggers a build. A successful build is promoted to a deployment, which is what your users see.
For now, rollback by reverting the offending commit and pushing. A full "rollback to deployment N" UI is on the roadmap.
If a build fails, the previously-live deployment continues serving. The build detail page shows the stage that failed and the error message.