An access log contains a record of all files which have been requested by the visitors while browsing your site. The list is thorough, so in case you have a webpage with two embedded images, for example, all of the three files shall be in the log, not only the page. An access log normally contains the date, the OS, the browser and the IP address for each and every file in human-readable form, so you can get an idea about the most popular files on your site. The log, that is also commonly referred to as "raw data", is an addition to the web stats you typically get with a hosting account, not a replacement. An illustration why you may require this kind of a log is if you wish to use some software on your computer system to prepare a report about the website’s general performance, but you don't want to use the regular graphs and tables that come with the server-generated site stats.