What are Power Query extensions?

In short, Power Query extensions are primarily pieces of M code that add to the global environment. Refer to Chapter 7, Conceptualizing M, to understand more about the global environment. Extensions are primarily used to create custom data connectors but can also be used to create a library of reusable custom functions.

These extensions come in four different file types (file extensions):

• m: This is a simple text file containing M code.
• Pq: This is a simple text file containing M code.
• mez: This is a standard ZIP file containing custom connector files. Can use a standard ZIP file and rename it from file.zip to file.mez.
• pqx: This is an Open Packaging Conventions (OPC) ZIP file containing custom connector files. Typically packaged using the System.IO.Packaging .NET library, this packaging format allows the digital signing of the file and is the format for Microsoft-certified connectors.

As noted, .mez and ...