XMP
An extensible metadata framework that stores descriptive data and editing instructions in a structured, readable form.
In depth
XMP can be embedded in a file or held alongside it, and it is the mechanism by which raw processing settings, crops and local adjustments are recorded without touching the original data. Because the format is text-based and documented, it is far more durable than a proprietary catalogue database.
Examples in practice
Copying a raw file and its XMP sidecar to another machine carries every edit across intact.