A small piece of JavaScript placed on a website that sends data to Google Analytics. The tracking code is what enables Google Analytics to report information about your audience, including how they got to your website, how long they stayed, and what they did while they were there.

Combining Email Marketing with Other Types of Marketing
Whether you choose to do your marketing online or offline, one thing does not change. This is the concept that no single marketing strategy will be as effective as a combination of two or more marketing strategies.