The catalogue is a register of metadata schemas that can be used for research data description. It includes both universal schemas (such as Dublin Core, DataCite, etc.) and subject-specific schemas.
Re3data is a registry of data repositories from all over the world. In addition to other descriptive information, the repository record also contains the metadata schema that the repository uses. Thanks to the Metadata Standards facet, it is easy to find out which schemas are most commonly used.
FAIRsharing records information about repositories and the standards that these repositories use.