What is unique about Fastlingo apps is the way vocabulary and grammar concepts are repeated at certain intervals until they are learned. It is a continuous progress from beginner to advanced where each sentence not only brings something new but reinforces things learned previously. The course covers the whole German grammar and teaches about 4500 of the most frequently used German words. The content is structured to provide a gradual increase in difficulty, with explanations at every step, ensuring a smooth and enjoyable learning experience.