Care to elaborate on that at all?
You should probably understand the basic fundamentals of file storage. Once a file has been marked deleted, it's not actually deleted. What happens is that the space that the file once occupied is marked safe to overwrite (by your laptop or whatever, or camera in this case).
If you decide you want to undelete something, providing another file has not been written over the space that the deleted file once occupied, you will be able to restore the deleted file. If it has been partly overwritten, you can sometimes salvage the data - but more often than not the file will be corrupted and you won't be able to recover it.
Hope that helps.