Often website owners need to add multiple code snippets to track their conversions, traffic, and gather other analytical data.
With Google Tag Manager you can easily add and manage all of these scripts from a single dashboard.
There are built-in tag templates for Google Analytics, Adwords, DoubleClick, etc. Tag manager also works with several third-party analytics and tracking platforms.
Apart from that, you can use custom HTML to add your own tracking or any other code that you want to add.
This saves you the time of adding and removing tags from your code and rather manage it from an easy dashboard.