Web Analytics
Simply put, web analytics means knowing what people are viewing and interacting with when they visit your web site and web pages.
Available analytical information ranges from the basic, "which pages are viewed most? " to the a more detailed, "how much do people spend on my web site's products and where are they located?"
Start with this brief overview from Wikipedia.
Google Analytics is a free service that allows users to enter code into each individual web page and track many characteristics of that page as people interact with it.
