With the Undo Checkout function, you can undo checking a document out without saving the changes on the server. In this case, you will lose all changes you made to the document during the checkout. This function is useful when you have checked a document out, made changes and saved the document, but do not want the changes to take effect. In other words, you want to restore the document to how it was before you checked it out.
If the document has never been checked in, it is deleted when the Undo Checkout function is used.