The Power Query Editor is the user interface that you have now learned is used to design and build data imports. However, you should also know that every transform you apply within this editor is actually, quietly and behind the scenes, writing an M query for you. The letter M here is a reference to the languages data mashup capabilities.

For simple solutions, it is unlikely that you will ever need to even look at the M query that is being written, but there are some more complex cases where it's helpful to understand how to read and write your own M. For the purposes of this book, covering just the Power BI essentials, you will learn how to find the M query editor within your solution and then understand how to read what it is doing for you. For the purposes of this example, you can open up any previously built example, however the screenshot used here...