And, of course, you can use the same technique going from the flash drive to your hard drive. And, here's something to be aware of. Suppose you drag a folder containing numerous files from the hard drive to the flash drive, then later you add more files to that folder on your hard drive or update some of the existing files. Then, to get the new and/or updated files copied over to the folder on your flash drive, you repeat the original dragging technique. When Windows sees that some or all of the files you are copying to the folder on the flash drive already exist on the flash drive (i.e. files of the same name are already on it), Windows will pause and ask you whether you want to overwrite the existing file on the flash drive, and it will show you the date and time both files were created so that you can decide whether to overwrite or not.
Of course, you can elect to overwrite all files during the procedure. However, if large files are involved, you might save some time by not overwriting where there has been no change in the file since that last copy. And, the same works in the opposite direction, going from flash drive to hard drive, in case you happen to work from the flash drive at certain times rather than the hard drive. It's a technique for synchronizing the two sets of files.