Every time you upload a file into a course (or do a course copy) it gets added to a file repository, similar to something you would find on a computer such as My Documents. In this case, all files are added to a section called, appropriately enough, Files.
All of that is well enough, but unlike a traditional computer file system, Blackboard does not handle Duplicate Files well. In this Knowledge-base Article, you will learn how to avoid duplicate files and excess bloat in your Blackboard Course.