It is common problem to select and delete object by accident and realize that the object is missing after you have done some more things on your drawing.
Other situation would be if you have deleted something and after a little time you realize that it would be good to have your object back.
Yes, we all know about UNDO command. We see it in every software and it is one of the most important commands in AutoCAD. However if we want to bring back last erased object, we would have to lose all other commands that we have used after deleting it.
The OOPS command, yes OOPS! What this command does is retrieving the Last Erased Object, without affecting any other newly placed object or command. On the other hand UNDO will retrieve the Last Command you have used.
OOPS command can be very powerful and useful I will try to create one little example just to help you understand it better:
Note: You can also use OOPS after BLOCK or WBLOCK because these commands can erase the selected objects after creating a block.
You cannot use OOPS to restore objects on a layer that has been removed with the PURGE command.