How can I undo a terminal command?

I have altered the default location of screenshots taken on my iMac. Origionally the screenshots were sent to my desktop.

I created a folder and named it screenshots. I then opened a terminal screen which was found in the finder, under utilities. Then I copied the following into the command line "defaults write com.apple.screencapture location". Then before clicking return, I dragged the folder I named "screenshots" into the terminal window. Then I typed "killall SystemUIServer" to reset the terminal and the changes took effect.

I am curious now, how to undo these changes if I want to?