It's just Word's backup copy. When you work on a document in Word, Word makes a "timed" backup of the document at regular intervals (which you can configure). In case the computer crashes or Word is not closed normally, you can find the document in Word's default backup folder, or when you next open Word, Word will tell you about the last backup copy and ask you whether you want to retrieve it.
Otherwise, once you exit or close Word properly in the normal way (so that the open document is properly saved and closed), the backup copy will disappear.
So if you save your Christmas Party Plan document and close the document, do a search again and you won't find the strangely named document.