What is a realm?
A realm is a part of Yanel which has its own configuration and repository. This allows you to run several subsites (which are independent of one another) in a single Yanel instance. For example, each department in your company can have its own realm. This allows one department to use its database as a content repository and another to use the filesystem to provide the content to Yanel.
Realms can also be nested, which allows you to have a subsite within a subsite. Continuing with the department example, one department could have its public file-based website within its realm and access its database for internal use in a subrealm.
Realms are registered within the realms.xml configuration file.