metadata are data about the data resource.
Metadata in Tabulify are also known as data definition.
For tabular data, there is two kind of metadata:
Metadata stores are system dependent.
On file system, the metadata definition depends on the file type.
For a file type that does not store metadata along its data, tabulify uses data definition file.
In a SQL database, the database has a metadata store and tabulify stores them there.