This call lets you queue a job to export a file from a project on the Platform into a volume. The file selected for export must not be a public file or an alias. Aliases are objects stored in your cloud storage bucket which have been made available on the Platform. The volume you are exporting to must be configured for read-write access. To do this, set the access_mode parameter to RW when creating or modifying a volume.
Essentially, the call writes to your cloud storage bucket via the volume. If this call is successful, the original project file will become an alias to the newly exported object on the volume. The source file will be deleted from the Platform and, if no more copies of this file exist, it will no longer count towards your total storage price on the Platform. In summary, once you export a file from the Platform to a volume, it is no longer part of the storage on the Platform and cannot be exported again.
If you want to export multiple files, the recommended way is to do it in bulk considering the API rate limit (learn more).
Learn more about using the Volumes API for Amazon S3.