Managed solutions are used to deploy to any environment that isn't a development environment for that solution. This includes test, UAT, SIT, and production environments. Managed solutions can be serviced independently from other managed solutions in an environment. As an ALM best practice, managed solutions should be generated by exporting an unmanaged solution as managed and considered a build artifact.
Additionally:
You can't edit components directly within a managed solution.
Reference: https://docs.microsoft.com/en-us/power-platform/alm/solution-concepts-alm