Explain what is meant by the process of transferring data between databases or their structures.

The process of moving data between databases or their structures is usually called data migration. It involves extracting data from one database, transforming it into the required format, and loading it into another database.

For example, when updating an application, it may be necessary to transfer data from an old database version to a new one with a modified schema. Migration tools or scripts are used to ensure data integrity and correctness.

In iOS, Core Data migrations are often used when the data model changes, and user data needs to be preserved during an app update.