Haha....I've had this happen to me before...I was like "What the heck?..."
Your Windows Logo Key (WLK) on your keyboard is stuck. Check here
for the list of Windows Logo Key keyboard shortcuts (among other keyboard shortcuts), including "WLK + M" for Minimize, "WLK + R" for the Run box, and "WLK + arrow key" for the various Aero Snap features.
Try giving your WLK a tap and see if you still get the keyboard shortcut behavior. If it still sticks, you may have to replace the keyboard. Do you have a built-in keyboard (laptop) or an external keyboard?
The first time this happened to me, I was baffled beyond all belief.
Then I noticed a pattern in the weird things happening when I tried to type (the arrow keys making the windows Snap tipped me off)....gave my Windows Key a tap and all was well again.
It was confusing, though, wasn't it?
to Bleeping Computer, by the way.