fileregister gives a file a permanent id — cached in a macOS bookmark and an xattr, but sourced from a plain JSONL index — so register resolve car-policy still finds the file after it’s renamed, moved to a NAS, or copied to a second Mac. A binder is a named set on the record, not a folder: the same PDF can sit in three binders without being copied or moved. register marshal packs a binder’s files and notes into a tar.gz that unmarshal rebuilds elsewhere, same ids intact.