What is Drush?
Drush, which means DRUpal SHell, is a shell interface that allows you to manage your Drupal site via a command line interface. Originally created for Drupal version 4.7, it has been maintained and updated up to the current Drupal version.
Why use Drush?
Using Drush will make administering your site much faster. You can also use it to manage multiple sites. Drush will also allow you to quickly install, backup, and restore drupal sites on your server. You can do many of the normal tasks within the command line that you would normally do via the user interface.