it checks if the `%%j` token from the FOR loop is empty.Though the better way will be to use double quotes intstead of a #
– npocmakaOct 17 '17 at 12:18
Because in no part of the question title, nor in the question body, you specify that this question is related to Batch files! You always should indicate what is the matter of the question; otherwise the readers have no idea of what you are talking about until read the `batch-file` tag, in the bottom line... I included the smiley to indicate that the link to the Wikipedia article is a joke (although it answers the question _as posted_: "What is the `#` used for?") with the hope that you realize that the question lacks important details...
– AaciniOct 19 '17 at 13:49
@Aacini I thought the tag is integral part of the question. Mentioning it in the title or body would be redundant, no? Nevertheless I still added it.
– RolandOct 20 '17 at 05:16