Aegir is a web hosting platform built for Drupal that allows managing multiple Drupal sites from a single server. It provides automatic backups, restoration, and cron jobs while centralizing administration. Drush is a command line tool used to manage Drupal sites from the command line by performing tasks like installing modules, enabling/disabling modules, and backing up databases. Aegir uses Drush and is designed to host many Drupal sites on one server through multisite functionality and installation profiles, but requires Linux knowledge and custom profiles to integrate fully.