How to get fields from taxonomy terms?
The entities aren't loaded by default (for performance reasons), but TermStorage::loadTree takes a $load_entities parameter:


  If TRUE, a full entity load will occur on the term objects. Otherwise they are partial objects queried directly from the {taxonomy_term_data} table to save execution time and memory consumption when listing large numbers of terms. Defaults to FALSE.


That will give you access to the fields. E.g.

$terms = \Drupal::entityTypeManager()
  -&gt;getStorage('taxonomy_term')
  -&gt;loadTree($vid, 0, NULL, TRUE);