that tells the LogManager to use this implementation of YourLogger, since the logger is asking for a Type in the constructor that is what we are giving it.
Other wise LogManager doesn't have any implementation other than NullLogger as per the default in source of Logging.cs
Now... when you want to get a variable to play with you use ILog _log = LogManager.GetLog(typeof(YourViewModel));
_log.Info("Blah Blah");