Shared and multiple calendars

Other Calendars appears when other organizations have granted your organization access to their calendars. There are calendars you've shared out, calendars shared with you, and mutual shares (both directions).

Multi-calendar must be enabled for your organization. When it's on, anyone who can manage requirements (Requirements: Manage, or an Administrator) can manage calendars, and roles can be granted access to specific calendars. A calendar can't be deleted if it's the default or has events. If you don't have the option to manage calendars, ask an administrator.