Discovers schemas on the remote system. These are tables, columns, object types, aspects, categories, content types, index fields, etc… Basically the types and metadata associated for any given system. Federation Servicestion Services unifies all of this into a Schema for easier mapping. Discovery makes mapping to and from your sources easier for data migration and ensures the data gets connected to the right fields.
Discovery connectors are responsible for discovering the schema, or the metadata about the repository. This will include content types and their associated properties.
A discovery schema can then be used to aid in creating Job Mappings or to simply find out what’s in the repository. Running a discovery instance will create a new version of the schema. Whatever version you select will be used when creating mappings.