Cloudant schema discovery process (SDP) scans a Cloudant database and intuits the implicit structures in your data. It then creates that proper schema in dashDB and copies the data over.
DashDB is built on a relational database, where the data is stored in structured relational tables. Cloudant stores JSON documents, where all the data is encapsulated in a single record. To move data between these two systems we need to be able to translate our JSON docs into a schema (or set of tables) that dashDB understands. This is exactly what the SDP does. It scans your Cloudant database and intuits the implicit structures in your data. It then creates that proper schema in dashDB and copies the data over.