Subscriptions can be either private or public. The difference between private or public is who can assign this Subscription to a Role.
A private Subscription can only be assigned to one or more Roles by a member of the same Role as the creator of the Subscription. Additionally, only Administrator type Roles can assign these Subscriptions.
A public Subscription can be assigned to a Role by any System Administrator or Group Administrator who has the ability to edit the Role.
For more information, see Assign Subscriptions to Roles.