Explain Google Tags in the easiest way possible.

I dare you to explain GTags in the easiest way possible to a newbie.

Can't do that mate, it too heavy. I'm stop using it long time ago, not because GTags, it fine, but too hard to understand what it is, now I used GTags only when my ads campaign on Google ads asking and I doing exactly what they ask for, but deep in my heart I even don't know what I'm doing, and I'm not see report or anything similar to it even it available for me.