Problem: You need to create an apex trigger on the contact object which trigger whenever a new contact is created or updated and update the description accordingly

TgrContactBeforeInsertUpdate.tgr

trigger TgrContactBeforeInsertUpdate on Contact (before Insert, before Update) {
for( contact c : Trigger.new )
  {
    if(trigger.isInsert)
    {
    c.description = 'contact created successfully by insert trigger ';
    }
    else if(trigger.isUpdate)
    {
    c.description = 'contact update successfully by else update block';
    }
   }
  }