Drush is a command line shell interface for Drupal which can be very helpful for all sort of automated tasks like backups, package management, updates etc..
Something I've always envied to WordPress was the possibility to update its core with a simple click.
Drush can do exactly the same, updating the core with one
click single "enter" thanks to pm-update.
The same command can update modules and themes as well.
This was just a simple introduction to Drush in case you didn't know it already.
Have a look at the official documentation to find out all Drush can do for you.