The GTM is in reference to Google Tag Manager. While building out the website, I decided that it would be nice to have some web site stats, and was just about to add “Google Analytics” plugin to my wordpress installation. Glad that I investigated a little more.
Google Tag Manager is a free product from Google that allows you to manage Google Analytics in a pluggable manner. Decide to change from GA to Adobe Analytics? No problem, just swap it out in the GTM.
Found a lovely plugin to help integrate GTM into my wordpress install, https://wordpress.org/plugins/duracelltomi-google-tag-manager/