Detail Page display using Command:link

<apex:param> is the child of <apex:commandLink>. Passing the record ID in the value of the param component and fetching it by currentPage.parameters.rId.

Here we have a visualforce page fetching the records by using a standardcontroller. On click of the commandlink,  the detail page of the record would be displayed.

Visualforce Page

<apex:page sidebar="false" standardController="DataLoadTest__c" recordSetVar="records">

  <apex:form >

      <apex:pageBlock >

          <apex:pageBlockSection >

              <apex:pageBlockTable value="{!records}" var="r">

                  <apex:column headerValue="Name">

                    <apex:commandLink value="{!r.Name}" rerender="out"                          status="mystatus">

                    

                      <apex:param name="rId" value="{!r.Id}"/>

                    </apex:commandLink>

                  </apex:column>

                  <apex:column headerValue="City">

                      {!r.City__c}

                  </apex:column>

                  <apex:column headerValue="Country__c">

                      {!r.Country__c}

                  </apex:column>

                  <apex:column headerValue="phone">

                      {!r.phone__c}

                  </apex:column>

          </apex:pageBlockTable>

          </apex:pageBlockSection>

      </apex:pageBlock>

    

      <apex:actionstatus id="mystatus" 

startText="loading.................">

          <apex:facet name="stop">

              <apex:outputpanel id="out">

                  <apex:detail subject="{!$CurrentPage.parameters.rId}"                        relatedList="false"/>

              </apex:outputpanel>

          </apex:facet>

      </apex:actionstatus>

  </apex:form>

</apex:page>