If you want to read a quick overview of this in Spanish, check my post about GTM at DoctorMetrics.
Google has just unveiled a new tool: Google Tag Manager. I have spent a few hours playing with it (both before and after official release.) And it’s awesome! Or at least, it has quite a lot of awesomeness, hidden behind a seemingly simple interface.
Its main feature is the fact that you can get away with just a piece of included code.