What is a Stat Counter
A stat counter (short for statistics counter, and also known as hit counter) is a piece of code which you can embed in your web pages to help you monitor site traffic. Stat counters can be found in varying levels of complexity, each serving a different purpose.
The basic counter
This code keeps count of how many times a page is visited. It counts each page load whether the visitor is new or returning, and whether the visitor is human or a <crawler>. If a user hits "refresh" ten times in a row on your front page, it will be counted as ten different visits. Also, if you place the same piece of code on different pages, it will count the sum total of visits regardless of which page was visited.
As you can imagine, a counter this simple will hardly provide you with an accurate picture of site traffic. Today, its main purpose is to display statistics to the visitors rather than to you, along the lines of "this site has been visited by 14,215 people". Code for basic counters usually comes with various graphics for displaying these statistics on your site.
Advanced counters
More advanced code will allow you to count unique visits (different users), to determine what sites they come from, and even to track their progress from page to page within your site. These statistics are rarely displayed to anyone but you. They give you a much more accurate idea of how many people reach your site, how long they stay there, how many pages they visit, etc.. From this detailed data you can deduce many things, like how relevant your content is to people who reach your site, how friendly your navigation system is, and more.
Most of these advanced stat counters will require you to open an account (sometimes for free) with the provider of the counter script. After embedding the code in your pages, you will be able to view the results at the provider's site.
The most famous of these advanced counters today is Google Analytics, a free service offered by Google with many powerful features for traffic analysis.