This is possible. Unless you have specific requirements, if you place your WAR or EAR into the JBoss deploy directory, it will create a context using the name of the file. So a file called MyContext.war will create a context called MyContext.
If you have specialised context needs, refer to this thread (covering non-default context mapping and virtual hosts):
http://www.jboss.org/modules/bb/index.html?module=bb&op=viewtopic&t= review the information in the JBoss 3.2.0 changes FAQ and the embedded Jetty FAQ for more detailed information on the basics.