Dired is a very useful file manager. Unfortunately it lacks a synchronization command.
dired-sync is designed to fill that missing feature.
NOTE: 2021: This package was last maintained in year 2014. There exists a MELPA package dired-rsync under much more current maintenance (2020-12).
drop dired-sync.el in your load-path and bind (suggested) C-c S key to dired-sync:
(when (require 'dired-sync nil t) (define-key dired-mode-map (kbd "C-c S") 'dired-do-sync))
Please have a look in dired-sync.el comments for further information.