Why use Google Tag Manager?
Google Tag manager simplifies tracking throughout your website. Its gives you a centralised area to create the actual implementation of your Webpage tracking. Google Analytics is a reporting tool which you can use Google Tag Manager to pass values to. The values can be used to create new segmentation of your data or create new sets of data within your reports. If you don't use Google Tag Manager your alternative is probably going to be hard coding tracking functionality within your web pages. This will usually end up very messy especially if you have a lot of tracking functionality and it can be easy to break the tracking on your pages if you have to change values on a lot of pages for some reason. Tag Manager version 2 is much better than the first incarnation with a simplified system for implementing and creating tags. Some of the main benefits of tag manager are as follows:
Element and attribute selection
Google Tag Manger takes advantage of things like ids and CSS selectors to target elements. Just like with CSS you can target a very specific element or group of elements within your page and do with the make-up of this element as you wish.
Data manipulation and creation
Advanced event triggering
You configure triggers which run specific functionality based on an event like the page loading, a specific link click, or a form submission. What makes it really powerful is you can create multiple conditions to trigger things like an event or a pageview.
New Analytics data and segmentation
You can send data to Google Analytics in many different ways, as a pageview, event, social action or many other things.
Integration with other platforms
Tag Manager is also tied into many other products from Google and others like Adwords and you can build tags to pass values to these platforms or track actions on them
Tag Manager auto updating
If you change the name of your tag, trigger, or variable its name will change automatically across any tags, triggers, or variables you are using it in.
URL's are a key part of any website. Tag Manager includes many default URL values like the full page URL or page path. You can pass these values to Analytics or compare then to other values within Tag Manager.