What is the purpose of the "other", "jboss-web-policy", "jboss-ejb-policy" security-domains in JBoss EAP 6?

Issue

• In the security sub-system what are the following the security domains defined by default "other", "jboss-web-policy", "jboss-ejb-policy" meant for:

The section of the standalone xml file is below:

<subsystem xmlns="urn:jboss:domain:security:1.2">
            <security-domains>
            <security-domain name="ImaRealm" cache-type="default">
                <authentication>
                    <login-module code="ima.code.ImaCustomLoginModule" flag="required" module="ima.code"/>
                </authentication>
            </security-domain>
             <security-domain name="other" cache-type="default">
                    <authentication>
                        <login-module code="Remoting" flag="optional">
                            <module-option name="password-stacking" value="useFirstPass"/>
                        </login-module>
                        <login-module code="RealmDirect" flag="required">
                            <module-option name="password-stacking" value="useFirstPass"/>
                        </login-module>
                    </authentication>
                </security-domain>
                <security-domain name="jboss-web-policy" cache-type="default">
                    <authorization>
                        <policy-module code="Delegating" flag="required"/>
                    </authorization>
                </security-domain>
                <security-domain name="jboss-ejb-policy" cache-type="default">
                    <authorization>
                        <policy-module code="Delegating" flag="required"/>
                    </authorization>
                </security-domain>
            </security-domains>
    </subsystem>

• For authentication of all requests that come to the server there is a third party SSO solution. For that configured the security domain "ImaRealm" is configured ,can the rest of the security domains be removed?
• How to secure application using ApplicationRealm user added using add-user.sh script?