All Google pixels including Analytics, Remarketing Tag, AdWords, DoubleClick, E-Commerce tags etc are replaced by this small piece of JavaScript. Marketers don’t need to bring in a webmaster anymore once it’s put into the website. That means that potential sales opportunities won’t be missed while the website code updates itself.
Google Tag manager user interface lets you put administrator and site tags directly from the account. The one interface can also manage multiple websites which means that while a company might have multiple website or AdWords accounts, it only needs one Google Tag Manager account.
You can check out Google Tag manager here.