I have a folder where I transfer home videos from a camcorder to. I find two files in this folder that are not videos...
What are these files, and can they be safely deleted?
You can safely ignore .fuse_hiddenXXXX files. It means a file was deleted but there is at least one software which is still using it, so it can't be removed permanently.
It will be done automatically when the relevant software stops using the file or exists. Such files are always gone after umount/reboot. This is how Linux and any Unix works but only FUSE exposes these files to the user.
These are likely files that were meant to be deleted but are somehow still in use.UBF
Those are just files that tell the camera to recognize these files as it's own and to view them. Delete these files and the camera will not recognize them. Keep them there, they are completely harmless.