The gc command garbage collects unused containers that have been forked. By default a container is considered unused if not run within the past 7 days.

Usage: turbo.exe gc <options>

<options> available:
      --all                  Include unforked containers for removal
      --all-users            Applies the configuration settings to all users
      --days=VALUE           Number of days until a container is considered unused
      --format=VALUE         Use the specified format for output. Supported values: json
      --trial                Run without deleting the containers
      --wait-after-error     Leave process open after error
      --wait-after-exit      Leave process open after it exits

The run or subscriptions commands forks containers when the base image is automatically upgraded to a newer release. The gc command removes older version of these forked containers.