Digital marketing made easier: Introducing Google Tag Manager
analytics.blogspot.co.uk
analytics.blogspot.co.uk
If you have money to spare, though, I'd recommend another solution. I've only briefly looked into Satellite but I'd say go with that over GTM. GTM has the normal Google problem of making things a bit too complicated, while with Satellite I was confident that I could hand off the account to a less technical member of our team and there'd be no problem making changes.
For those interest to know more, the Satellite link:
I was somewhat confused what it was talking about when it referred to tags - it primarily means snippets of Javascript. Things such as your Google Analytics snippet, Facebook Like button snippet etc.
This is for things like Google Analytics, Compete, QuantCast, AdWords/DC/etc remarketing, MixPanel/KISSmetrics PV events, ad trackers... JS code that tags your visitors for tracking and remarketing purposes, not code with output.