Awful explanations, they just assumed you fully understood the topic without any practice or exercise of it (if you're using the free subscription service that is), and unlike other coding apps, they don't even bother telling how and why you're wrong while coding, it's just overall terrible. The cherry on top though is the premium subscription, it's pretty much required if you want to make the most out of this app. Just avoid this app, there are better alternatives than this.