Format and quick format both write the directory entries for a drive recording all the sectors available for use on the drive. Format additionally runs a check of each and every one of those sectors confirming that each one is readable, quick format does not so problems may exist on the drive which will not be detected by quick format. Delete if you're referring to file delete, does not write the directory entries at all, it simply sets the entries for the file(s) being deleted to empty so that all of the sectors which they occupied show as being available. Deleting a logical drive of partition releases the sectors allocated to the drive and shows them as unallocated. None of these processes, format, quick format or delete (partitions or files) physically removes any data from the drive and it is quite easily recoverable to anyone with the necessary skills and tools.