You can gain a Catamaran Qualification by
(i) Completing the NauticEd Catamaran Sailing Confidence course online
(ii) logging at least 3 days as skipper or 7 days as crew on a 38 ft (11.5m) or greater sized catamaran
(iii) being Bareboat Charter Master Rank with level III experience
It means you have enough knowledge, skills, and experience to qualify to charter a catamaran. Please check with your yacht charter company first as to their specific experience requirements. Some still may want to do a few hour check out of your competence in handing the rented Catamaran.