Phoenix Changeset

Thx, so to see if i get it right ,according to this Phoenix why not show changeset errors? and this Phoenix.HTML.Form has two errors fields when validating?. The form_for helper receive the changeset, check if there is a action, is there is a action, put the errors of the source into the error field of the form and if there is not action, just leave that field empty. So when error_tag is called, check in the error field of the form?