How does the key picks up correct resource from tiles-def.xml

Question

I have the following code snippet where the key is defined in tiles-def.xml. I want to know how the key correctly maps to tiles-def.xml rather than picking up the resources for the key from application-resources.properties

struts-config.xml

<action
          path="/POShowSearch"
          type="com.inx.omx.lc.web.actions.POShowSearchAction"
          scope="session"
          name="ViewSearchFormPO"
          input="crp.lcpo.view">
<forward 
          name="Success"   
          path="crp.lcpo.view.result" redirect="false" />
</action>

tiles-def.xml

<definition name="crp.lcpo.view" extends="crp.main" >
        <put name="body" value="/po/poSearch.jsp" />
</definition>
<definition name="crp.lcpo.view.result" extends="crp.main" >
        <put name="body" value="/po/poViewList.jsp" />
</definition>