Drush is a command line tool for Drupal administration & development.
If you are not using Drush yet, it's definitely a must-use tool but to get you warmed up this session will be your must-see intro for Drush.
What can Drush do?
A lot. And very fast!
Download modules, themes, libraries, and updates in milliseconds! Run or import backups in a snap! These are just a couple basic examples of this Drupal Ninja tool.