module is object defined automatically by Node.js. This allows you to copy and paste the line into each file and leverage your filename. The file name matching is done with module.id or the filename with the working directory and trailing '.js' removed. If you don't want automatic module names, replace it with your desired string name. Arguments are not inspected unless the log level allows for printing of the statement. This avoids unnecessary object serialization calls before submitting your log statements.