All the columns in xTuple's External Vendor Catalog follow the trade service naming conventions. Documentation of these standard naming conventions are provided by trade service with your subscriptions. If you do not have the Trade Service Guide, please contact Trade Service to obtain a copy. Trade service also provides a form to fill out indicating which vendors you are currently subscribed to. This form is also available from trade service.
A map of all trade service related fields can be found in the conversion mapping document distributed through the xTuple site on GitHub.