Use of Param Tag and Command link:-

 We have another scenario, i.e As users select the account, by clicking the name of the account, a message is displayed alerting which account was selected.

 <apex:page controller="fifthinterview">
  <apex:form >
      <apex:pageBlock title="Interview Five" id="Test">
         <apex:pageMessages > </apex:pageMessages>
     
         <apex:pageBlockTable value="{!Data}" var="acc">
            <apex:column >
                <apex:commandLink value="{!acc.name}" action="{!Calling}" reRender="Test">
                    <apex:param name="Txt" value="{!acc.id}"/>
                </apex:commandLink>
            </apex:column>
            <apex:column value="{!acc.Name}"/>
            <apex:column value="{!acc.BillingState}"/>
            <apex:column value="{!acc.Phone}"/>
            <apex:column value="{!acc.Website}"/>
          </apex:pageBlockTable>
      </apex:pageBlock>
  </apex:form>
</apex:page>

 public class fifthinterview{

    public fifthinterview(){

        ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.INFO,' Select an Account by Clicking its name.'));

    }

    List<Account> Varacc;

    public List<Account> getData()

    {

        string str1=Apexpages.currentpage().getParameters().get('id');

        Varacc =[Select id,Name,BillingState,Phone,Website from Account];      

        if(varacc.size()>0)

        {

            return Varacc;

        }

        return null;

    }

    public void Calling() {

        string str1=Apexpages.currentpage().getParameters().get('txt');

        Account varacc=[select id,name from Account where id=:str1];

        String ex=varacc.name;

        {

             ApexPages.addMessage(new ApexPages.Message(ApexPages.Severity.INFO,' You have Selected--> '+varacc.name+'-Organization'));

        }

    }   

}