When designing material intended to be printed, your design has to appear in the “bleed area”.
Bleed is a printing term that is used to describe a document which has images or elements that touch the edge of the page, extending beyond the trim edge and leaving no white margin. When a document has bleed, it must be printed on a larger sheet of paper and then trimed down.
So basically, make sure that any part of your design that is intended to be printed (i.e. background layers/colors/textures), extend into the bleed area. Otherwise, if you didn’t do this, if someone buys your template and tries printing it, there will be an empty white border on everything printed instead of your background design/color. This would be a costly error and it would need to be corrected and reprinted.
Here’s an image to explain further:
See the following article for more information:
Hope this helps, good luck with your update!