This is intended for those that do not have access to their server logs. The plugin will create a log file in the base of your elgg install called error_log.txt (as long as the permissions allow for this). Into that file will go all the warnings and exceptions that normally go to the server log. It does not catch Elgg Debug statements when those are turned on because of how they are implemented. In the start.php I added some useful information that you should read through. You can also change file locations or names in start.php. It's simple code so take a look.