A multisite configuration is used when a web server is associated to different domain names, and you want the web site to appear different when accessed from different domains. (If you want the web site appears the same in both the domain, there isn't any special Drupal configuration to follow.)
Suppose that your web site answers to example.com, and example.org. You can have two different settings.php files:
- sites/example.com/settings.php for example.com
- sites/example.org/settings.php for example.org
In the case those files are not found, Drupal would use the default one (sites/default/settings.php).
The same can be done for subdomains.
On your Mac, you should edit your hosts file (/private/etc/hosts) to add something similar to the following one:
# Host Database
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
In this case, the following files would be used:
- sites/first.localhost/settings.php for first.localhost
- sites/second.localhost/settings.php for second.localhost
If those files are not found, Drupal would look for the following ones (and other files as well):