For more information about the statistics generated and this webpage see Administrator's Guide - Statistics.
Log files are discussed in the System Architecture Overview here.
Watching log files can be useful for gathering statistics not already compiled, watching performance, and discerning source of errors. If an error arises, check the corresponding log file for a stack trace that gives details of an error. If the stack trace does not give enough information to fix the problem, email the Variations Development Team with the symptoms and the full stack trace.