A catalog is a container for vApp templates and media files in an organization. Organization administrators and catalog authors can create catalogs in an organization. Catalog contents can be shared with other users or organizations in the vCloud Director installation or published externally for access by organizations outside the vCloud Director installation.


vCloud Director contains private catalogs, shared catalogs, and externally accessible catalogs. Private catalogs include vApp templates and media files that you can share with other users in the organization. If a system administrator enables catalog sharing for your organization, you can share an organization catalog to create a catalog accessible to other organizations in the vCloud Director installation. If a system administrator enables external catalog publishing for your organization, you can publish an organization catalog for access by organizations outside the vCloud Director installation. An organization outside the vCloud Director installation must subscribe to an externally published catalog to access its contents.


You can upload an OVF package directly to a catalog, save a vApp as a vApp template, or import a vApp template from vSphere. See Create a vApp Template from an OVF File and Save a vApp as a vApp Template to a Catalog.


Members of an organization can access vApp templates and media files that they own or that are shared with them. Organization administrators and system administrators can share a catalog with everyone in an organization or with specific users and groups in an organization. See Share a Catalog.


Source: https://docs.vmware.com/en/vCloud-Director/9.5/com.vmware.vcloud.tenantportal.doc/GUID-6424C4A7-EA95-49A0-B673-9DDB971AB566.html