Drush commands are commonly run in the Drupal docroot, the directory where Drupal's files live. This is a relatively simple task on your local development environment. But if you're working on multiple sites and each of those sites has one or more remote environments that you connect to via SSH, workflows quickly become complicated. Creating and using Drush site aliases allow you to run Drush commands on any site, local or remote, that you have credentials to access, from any location on your computer that has access to a Drush executable.