I am learning about GTM(google tag manager) so i didn’t judge between gtm and google analytic and how it works.
Please spend some times in web search as like google hope you will get answer.
Basically GTM can hold multiple tags, such as Google Analytics, Google Ads Remarketing, Google optimize etc. Each of this platforms provide you with a script. If you use each of this individually you’ll end up with multiple scripts on your website, which can slow down the loading speed. But with GTM you can just paste one single script that holds all the other script codes. You can modify all the events and triggers of the scripts directly in the GTM dashboard.
The easy way to think of GTM is a single container that holds multiple platforms.
I got the point.