Tracker This is the term I use for a service which does not display the count on your page, but provide you with an analyzed, statistical report. The common misconception is that it is a programming language. It is not a programming language, but rather a way for programs to communicate with eachother and the web. Server Logs Server logs are something that your server creates as a huge, raw record of everything that anyone does on your web site. You need some kind of access to your server in order to look at them.
Banners usually consume vast amounts of valuable web design space.
If they come with a counter or tracker, then they a major design embarassment. In my opinion, almost no amount of statistics could mitigate the design sacrifice of a banner. Avoid at all costs. The 'hidden' Counter is almost always a feature of hosted counters. It is usually a tiny, transparent gif which is used in the place of some sort of graphic which a user might see.