DOCS-2315: adds blurb about rename to rename tutorial intro

Author: schmalliso

source/tutorial/rotate-log-files.txt

@@ -40,7 +40,11 @@ signal from the operating system.
 Log Rotation with ``--logRotate rename``
 ----------------------------------------
 
-The following steps create and rotate a log file:
+Log rotation with :option:`--logRotate` ``rename`` is MongoDB's standard
+approach to log rotation. With ``rename``, :program:`mongod` or
+:program:`mongos` renames the current log file by appending a UTC 
+timestamp to the filename, opens a new log file, closes the old log file,
+and sends all new log entries to the new log file.
 
 .. include:: /includes/steps/log-rotate-rename.rst