Drush Make allows you to build a Drupal site from a a set of instructions, letting Drush download and install Drupal core and modules. This allows you to describe a Drupal site installation in a simple text file.
Drush Make can:
- Download Drupal core and contrib modules from drupal.org
- Checkout code from git, svn, etc. repositories
- Download tar/zip files (for libraries or modules)
- Download and apply patches