I have word docs on my desktop. When I click to drag the doc into a folder on my desktop...it "copies" the file instead of "moving" it into the folder. How do I stop this from happenning? I am new to all this 365 stuff.
It depends on the target. Within the same drive, it defaults to move. Between drives, it will be a copy operation. @Ricardo Viana gave you the steps to override this behavior above.
You could also use the right-mouse button to click and drag. Then, when you release, you'll be given the option to "move here", "copy here", etc.