Chamilo hides (within its many treasures) a discrete but practical feature in case you use your Chamilo portal for several categories of users, for which you have to consider making the portal available with a second domain name, another visual aspect and a pre-selection of only a few users and courses. An independent space sharing some of its content and all of its code, if you will.
For example, you might want to provide one Chamilo portal on http://one.campus.org/ and another one on http://two.campus.org/. Even if these are separate portal, you will probably have the same administration team managing all these, so it makes sense to share both the database and the files directory. This way, you even get to distribute users and courses over all portals as you please.
For those familiar with Drupal, this is not the same as a multi-site configuration, as Chamilo multi-url shares the database between all instances. It does provide multiple portals, but it is also more tightly bound through the database.