I am reading about web analytic and came across GTM and GA.
It seems that GA is a service provided by google which generates reports and statistics on website traffic. As per my limited understanding in order to generate this reports we need to perform some type of tagging at our end.
It also looks like that in GTM also we need to add some tags in our website.
So, if both GA & GTM are related to tagging what is the difference between them and why do we have two different products by google.