I have to travel to Geel, Belgium from Geneva, Switzerland. I will go by plane to Brussels and then I will the train(s) to Geel. Searching in Belgian Rail, I came accross a special ticket which i called the Diabolo Fee. i searched around to see, what exactly is that ticket and if it suits my needs, but I couldn't find any relevant and useful information.
Does anyone have any idea whatsoever on what exactly is that ticket and if I am able to use it to travel to Geel?