changing display depending on fields value I want to change how a field value can be displayed to the front-end user,

For example I have an Article content type which have a priority fields,
this priority can be either low or high as a value...

so I want when the priorty is high, my displayed view show me an image icon instead of the high value.
Another approach is to use MY_THEME_preprocess_node(&amp;$variables) in template.php and build your logic according to $variables array elements (e.g. $variables['field_priority']). Example:

function MY_THEME_preprocess_node(&amp;$variables) {
  if($variables['type'] == 'page') {
    $priority = $variables['field_priority'];

    if($priority &gt; 0 &amp;&amp; $priority &lt; 2) {
      // do_first_logic()
    }
    elseif($priority &gt; 2 &amp;&amp; $priority &lt; 4) {
      // do_second_logic()
    }
    // .... so on
  }
}