The World Selects tournament series is broken into two separate skill levels — ELITE and AAA. The World Selects Invitationals are for elite-level, top spring hockey programs and are invite-only. World Selects Trophy events are AAA-level, open to all players and teams capable of competing at that level.
There is a relegation/promotion relationship between the WSI and WST as well. A strong showing at the AAA tournament, and teams could be promoted to the Elite event the next year. Can't quite compete at the elite level? Drop down to the AAA tournament for a more balanced event.