You need a drone license for drones that weigh more than 250g. There are 2 courses: for drones in the open category A1/A3 and for drones in the open category A2. In these courses, you learn how to fly with your drone. For drones in the open category A1/3, you follow a less extensive course because these flights are less risky. If your drone is in the category A2, you need the more extensive course. It depends on the weight and the Cx label among others which category applies to your drone. Check which course you need for your drone. Once you successfully complete the course, you can request a drone license or flight certificate from the RDW.