Added some more info about the aws_s3 module's overwrite option (#31819)

lib/ansible/modules/cloud/amazon/aws_s3.py

@@ -101,7 +101,10 @@ options:
   overwrite:
     description:
       - Force overwrite either locally on the filesystem or remotely with the object/key. Used with PUT and GET operations.
-        Boolean or one of [always, never, different], true is equal to 'always' and false is equal to 'never', new in 2.0
+        Boolean or one of [always, never, different], true is equal to 'always' and false is equal to 'never', new in 2.0.
+        When this is set to 'different', the md5 sum of the local file is compared with the 'ETag' of the object/key in S3.
+        The ETag may or may not be an MD5 digest of the object data. See the ETag response header here
+        U(http://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html)
     default: 'always'
     aliases: ['force']
     version_added: "1.2"