Use it for the module for running a group of affiliated sites from one installation and a single shared database.

The Domain Access project is a suite of modules that provide tools for running a group of affiliated sites from one Drupal installation and a single shared database. The module allows you to share users, content, and configurations across a group of sites such as:

  • example.com
  • one.example.com
  • two.example.com
  • my.example.com
  • thisexample.com
  • example.com:3000

By default, sites share all tables in your Drupal installation. The Domain Prefix module allows for selective, dynamic table prefixing for advanced users.

Reference