How to get taxonomy term name/label from a field?
The field only stores term IDs. So either get the term ID and load the term from it or load the referenced entities directly.
/**
 * Implements hook_entity_presave().
 */
function MYMODULE_entity_presave(\Drupal\Core\Entity\EntityInterface $entity) {

  if ($entity instanceof \Drupal\node\NodeInterface &amp;&amp; $entity-&gt;bundle() === 'MYBUNDLE') {

    if ($field = $entity-&gt;get('field_MYFIELD')) {
    
      if (!$field-&gt;isEmpty()) {

        $label = $field-&gt;referencedEntities()[0]-&gt;label();
        // dpm($label);
        // Code on...
      }
    }
  }
}

Consider installing Devel. It gives you some handy debugging helpers like dpm($some_var) to dump variables into core's status messages block so you can inspect them easily.