A program that takes a server's "raw" log file data and summarizes it into easily-understood reports.

Many free or inexpensive log analyzers exist to provide high-level summaries of website activity. More expensive log analyzers exist to provide actionable information like visitor click-path trends (for design) and sales-by-referrer (for marketing).

You host many provide a log analyzer service as part of your hosting plan. As long as you have access to the raw log files, you can download them for current or future use with any other log analyzer programs.