Superbly means extremely well — so well that it deserves real praise. It is an adverb, so it tells you how something is done or how good a quality is. You use it with verbs ('she sang superbly', 'the team played superbly') and, very often, in front of an adjective or a past participle to lift it high: superbly written, superbly trained, superbly fresh, superbly organised. It is warm and enthusiastic, and it sits at the top of the scale — above 'well', above 'very well', close to 'brilliantly' and 'magnificently'. Because it is strong, using it too often makes writing sound like an advertisement, and in fact food writing, travel writing, and reviews use it constantly. In casual conversation between friends it can sound a little grand; people are more likely to say 'really well' or 'amazing'. One thing to notice: it is almost always positive. You would not normally say 'he failed superbly' unless you were joking, and the joke depends on hearing the mismatch.