Sometimes, it may be required to include a folder into a website which is located in another place than the htdocs folder on the server.
In this case, a Virtual Directory can be created, eighter with a link that points to this directory:
ln -s ../source/dir alias_name
or with a Virtual Directory Entry in the Virtual Hosts config (httpd.conf):
Alias /image /ftp/pub/image
<Directory /ftp/pub/image>
Order allow,deny
Allow from all
</Directory>
Source:
http://httpd.apache.org/docs/2.0/mod/mod_alias.html