Some trades (cosmetician or hairdresser, plumber, electrician for examples) require licensing before you can legally work in them. The idea is that working in these trades requires some skill to prevent harm - an unlicensed person wiring their own home could burn it down, an untrained cosmetician might not thoroughly sanitize instruments between clients, etc.. The provinces make sure that people practicing in these trades - or in licensed professions such as medicine, law, or teaching - have the education and skills to do it safely, and issue licenses to those they deem qualified to practice those trades or professions. The provinces or country also decide which trades and professions need licenses and which don't.
The question is asking those whose NOC corresponds to a licensed trade whether they have already obtained the required license to practice in Canada. If you have an NOC that indicates you are a plumber, for instance, it might give you an advantage to already have the license that would allow you to practice your trade in Canada immediately on receiving your pr.