Registries and catalogues are used both to publish and search through metadata collections. They help document and find descriptive information about existing data and services.
These directories can also harvest metadata from other registries. The Open Geospatial Consortium (OGC) makes a distinction between "catalogue" and "registry" by stating that a registry is a specialized catalogue maintained by an official entity in compliance with access and content management procedures and policies (ISO 19135 and ISO 11179-6 standards).
For more information, see Section 6. Data Sharing.