Dragging edge of desktop makes folders and files "hidden" on MacBook
I don't know if this has something to do with an external application or something, but when I go to my desktop and move my cursor to the very edge of either the left or right screen, the mouse changes to this left and right arrow "⬌" . Instead of just being able to click, hold, drag and select items on my desktop, with this feature I am apparently able to hide everything I drag the arrow around.
It's almost like it's producing what my wallpaper looks like behind the folders, but over them instead. It's just bizarre. See the video I took here. https://www.youtube.com/watch?v=8WT7z_ygBkY
If anyone knows about this, what is it called? Is there a "quick reset" in case I can't find the arrows or the starting point for making the files on my background practically invisible?
[Re-Titled by Moderator]
MacBook Pro 15″, OS X 10.11