An error log is a listing of the error messages and warnings that displayed for one reason or another while your visitors were looking through your Internet site. Such a log contains raw info about the way the web server has handled requests a number of situations. An error message may appear if, for instance, a link leads to a site or a file that isn't on the web server, if the code on a specific page cannot be processed, if anyone is trying to access the site or its back office through an IP address that is blocked by an .htaccess rule and many others. The information in the error log includes the IP address of the site visitor, what error message showed up and the root cause for the web server to show it, the full path to the file that caused the error and the specific time of the event. Having this info will help you learn if any part of your website has an issue, which you can then deal with. For that reason, your visitors will have a better experience and you'll optimize the website for maximum performance.