The difference between standalone and domain reflects in the filesystem of the application server, as shown in the following diagram:
As you can see, the AS 7 filesystem is divided into two main parts: the first one is pertinent to a standalone server mode and the other is dedicated to a domain server mode. Common to both server modes is the modules
directory, which is the heart of the application server.
JBoss AS 7 is based on the JBoss Modules project, which provides an implementation of a modular (non-hierarchical) class loading and execution environment for Java. In other words, rather than a single class loader that loads all JARs into a flat class path, each library becomes a module, which only links against the exact modules it depends on and nothing more. It implements a thread-safe, fast, and highly concurrent delegating class loader model, coupled with an extensible module resolution system, which combine to form a unique, simple, and powerful system for application...