What is a Published data source?

A published data source is a data connection saved to Server or Cloud as its own object, separate from any workbook, and reusable by many workbooks.

It carries everything defined on it: joins, calculated fields, field renames, default formatting, extract settings and its refresh schedule.

The advantage over an embedded data source is single-point maintenance. A schema change or a corrected calculation is fixed once rather than in every workbook, and everyone is working from the same definitions.

It is also where row-level security belongs, since a data source filter on a locked published source cannot be removed by a workbook author.