Child Row - Data object "d"?

Hey,

This is a complete noob question, but.... I'm trying to install child rows on a table. I'm following the example here (https://datatables.net/examples/api/row_details.html), but I can't work out what to replace "d" with in the first ,js function.

Code here: https://jsfiddle.net/dpgwqxL9/#&togetherjs=LacK5nTenu

My apologizes for the stupid question!