Code snippet that can help you to get taxonomy terms of a vocabulary in Drupal 8.
Load single term
$term = \Drupal::entityTypeManager()->getStorage('taxonomy_term')->load($tid);
$title = $term->name->value;
Load Multiple terms
$query = \Drupal::entityQuery('taxonomy_term');
$query->condition('vid', "tags");
$tids = $query->execute();
$terms = \Drupal\taxonomy\Entity\Term::loadMultiple($tids);
foreach ($terms as $term) {
var_dump($term->name->value);
}
