Can someone explain the interceptor statement?

[Jeshu Jayanthe]

Dear Friends,
I am new to Struts 2.0. Can someone please explain the below set of statements?

<action name="aliasing" class="demo.AliasAction">
<param name="aliases">
#{'username':'loginid','pwd':'password'}
</param>
<interceptor-ref name="alias" />
<interceptor-ref name="logger"/>
<interceptor-ref name="basicStack" />
<result name="success">/Success.jsp</result>
<result name="error">/Alias.jsp</result>
<result name="input">/Alias.jsp</result>
</action>

Thanks & Regards,
Jeshu

[David Newton]

It's doing a parameter renaming: they're coming in as "username" and "pwd" but being set on action properties "loginid" and "password".