Google Tag Manager or GTM is a free service from Google which facilitates work with HTML tags on websites or in mobile apps.
Google’s tag manager will be a great helper for those who can’t afford to hire a developer. To work with GTM, you only need to hire a programmer once — to install Google Manager code on website pages. You can do all the other work yourself with the help of ready-made templates.
Tag manager works on the principle of chain reaction. That means that performing a certain action with the specified parameters triggers a tag, which, in fact, sends you data for analysis.
Obtained data is imported into one of the analytics services, such as Google Analytics. This will allow you to analyze advertising campaigns, test individual elements on the website, and as a result — adjust promotion strategy of your brand.