This information only applies to organizations on the Pro and Enterprise plans.
Managed modules provides a convenient way to access commonly used community modules directly from your own hosted BSR. Buf keeps these modules up to date and syncs them to your instance automatically, just like we do for https://buf.build. You can see which modules are included by visiting the bufbuild/modules GitHub repository.
If you encounter any problems with your BSR instance's managed modules, contact Support or your Buf representative.