Steve SimmondsQuery Folding ... what !
If you're starting with Power Query and you're trying to understand or explain the concept of Query folding, this article is a great starter as it covers folding indicators, step scripts, query plans and more...
One of the most powerful capabilities of Power Query and the M Language is Query Folding
https://powerquery.microsoft.com/en-us/blog/introduction-to-practical-query-folding/