The planetscale_rails gem provides a collection of Rake tasks that help manage the schema of a Rails application, allowing developers to ship changes without downtime. The workflow uses PlanetScale's git-like database management system to introduce a new branch for making schema changes, which are then deployed as "deploy requests" to production with no downtime risk. This approach separates schema changes from code changes and automates the process, reducing the risk of errors or downtime. By using this workflow, developers can ensure that their Rails application is more reliable and efficient, while also saving time in the long run.