Visibility indicates the privacy setting of the item, based on the user's set visibility preference. If a visibility tag is included when information is posted via the API, it will be ignored. Rather, the information will be posted per the user's default visibility preference as set in their account preferences.
Public items can be read by anyone via the API and are shown on the researcher's public record, Trusted party items are only returned via the API to clients who have read-limited access; they are not on the researcher's public record. Private items are visible only to the researcher and the source of the item – the only private items returned via the API are those which were added to the record via your integration. More about visibility settings in the ORCID Registry.