sample CRUD application question

[Bhaarat Sharma]

I was looking at the CRUD sample application in struts2

http://struts.apache.org/2.0.14/docs/crud-demo-i.html

in one of the jsp's they have this code

<s:url action="crud!delete" id="url">
                    <s:param name="employee.employeeId" value="employeeId"/>
                </s:url>

and some part of the struts.xml is:

        <action name="crud"
class="com.aurifa.struts2.tutorial.action.EmployeeAction" method="input">
            <result name="success" type="redirect-action">index</result>
            <result name="input">/WEB-INF/jsp/employeeForm.jsp</result>
            <result name="error">/WEB-INF/jsp/error.jsp</result>
        </action>

I am lost as to why <s:url action="curd!delete"

shouldnt the action be just "crud" what does the exclamation mark and delete
do?? is that a shorthand for something or is that just an action name and if
it is an action name then why is it not defined in struts.xml

Thanks!!