What JSON is
JSON is a text format for nested data: objects with named keys, arrays, strings, numbers, booleans and null. It has no date type and no comments.
Every web API, most configuration files and anything that talks to JavaScript.
What DAX is
A DAX DATATABLE expression that defines a table inline in a Power BI model.
Power BI report authors.
What changes when you convert JSON to DAX
Four shapes all read correctly: an array of objects, an array of arrays with a header row, an object of column arrays, and an object keyed by row id. A single wrapper key holding the array, which is how most APIs reply, is unwrapped automatically. Nested objects are flattened one level into dotted keys; anything deeper is kept as JSON text in the cell, because a table cannot hold a tree.
All columns are declared as STRING. Change the type declarations by hand if you need numeric columns.
What carries over from JSON to DAX
JSON records 3 things about a table that DAX has no way to hold.
An empty cell and a missing one are the same thing in DAX, so a null and an empty string in the JSON both come out blank and can no longer be told apart.
JSON can hold a value that is itself a list or an object. DAX has only flat cells, so nested values are flattened into one cell rather than being spread across columns.
A line break inside a cell ends the row in DAX, so line breaks are replaced rather than carried through.
DAX marks header cells differently from data cells, so the keys are lifted out and written once as a marked header row rather than repeated on every row.
Both formats record types, so numbers, booleans and nulls survive as themselves rather than as text.
The identifier 007 comes out of the DAX as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a DAX file goes wrong.
The quotes around Jonah "Jo" Pryce are escaped with a backslash in the DAX.