Basically It stands for Multi Pilot License, Designed to reduce the amount of Hours to allow Graduate to gain Flight crew license to work at an Airline flying Multi Crew Aircraft like A320. An MPL holder usually has to do extra training to fly Single crew type's but most student's are doing this with Muti crew Aircraft job in mind or are under sponsorship from an Airline. Usually MPL is around 160 hrs and some hrs can be counted in Sim, The Countries I worked as an approved CPL flying Instructor before would normally require 250 hrs total etc to issue the Professional Ticket.