JBoss server configurations
Fundamentally, the JBoss architecture consists of a JMX MBean server instance (the "microkernel") and a set of pluggable component services -- the JMX MBeans. This makes it easy to assemble different configurations and gives you the flexibility to tailor them to meet your requirements. You don't have to run a large, monolithic server all the time; you can remove the components you don't need (which can also reduce the server startup time considerably) and you can also integrate additional services into JBoss by writing your own MBeans. You certainly don't need to do this to be able to run standard J2EE applications though -- everything you need is already there. You don't need a detailed understanding of JMX either but it's worth keeping a picture of this basic architecture in mind as it is central to the way JBoss works.
Within the server directory, there are three example configurations: all, default and minimal, each of which installs a different set of services.
default: The default configuration is used if you don't pass any parameters to the run script. It contains everything you need to run a stand-alone J2EE server including web services.
minimal: the bare minimum required to start JBoss. It starts the logging service, a JNDI server and a URL deployment scanner to find new deployments. This is what you would use if you want to use JMX/JBoss to start your own services without anything else from J2EE. This is just the bare server -- there is no web container, no EJB or JMS.
all: starts all the available services. This includes the RMI/IIOP and clustering services and the web-services deployer which aren't loaded in the default configuration.