Google Analytics' e-commerce tracking is a sophisticated sales dashboard tied in with Google Analytics' metrics. It extends regular sales reports to a report that can help increase your sales by analyzing all its metrics.

How E-commerce Tracking Works

E-commerce tracking is a JavaScript snippet placed on the post-checkout page. This snippet sends general transaction data to Google Analytics. To be able to send transaction data it needs to integrate with your shopping cart. The JavaScript snippet has four parts: setup and pageview, transaction, items purchased, and executing the script.

Setup Ecommerce Tracking

Setting up ecommerce tracking is dependant on the shopping cart engine that's being used. We've outlined a general guidance for PHP, Magento and WP e-Commerce.

Step 1: Turn on ecommerce tracking

1. Login to Google Analytics
   
2. Select your website profile
   
3. Go to Admin section
   
4. Go to Profile Settings section
   
5. Set E-Commerce tracking to Yes
   
6. Click Apply

Step 2: Install the script on your website

Wordrpess WP e-Commerce:
For Wordpress WP e-Commerce all you need to do is install this plugin: //wordpress.org/extend/plugins/google-analytics-e-commerce-tracking-for-wp-e-commerce/

Magento:
As of Magento version 1.4 Google Analytics ecommerce tracking is built-in. A step by step guide can be found here: //www.magentocommerce.com/knowledge-base/entry/setting-up-google-analytics

Other Shopping Cart Engine/PHP Implementation:
For an general idea of how to setup the script look at the attached example file under the resources tab.

Additional reference:
https://developers.google.com/analytics/devguides/collection/gajs/gaTrackingEcommerce#General