A log file is a standard type of computer file – often readable with a simple text editor but sometimes in a proprietary format. It contains a simple diary style list (log) of all the events of a certain type or types that have occurred during a specified period.
A webmaster may set the server to keep an error log file for example. This file will record any error messages the operating system for the server generates. In the event of an unusual activity – for example an effort to hack into or break the server – the webmaster can review this file for evidence of the techniques used or the problems that occurred with a view to fixing them.
User logs are also a useful way for webmasters to monitor the way their end users are using their content. Understanding who clicks where and how they came to find the stie are also useful information that might be found in a user log. More advanced analytics applications may store and monitor significantly more information (such as Google analytics) but the principle is the same – they log information about users in a file for a specified period for future reading and analysis.