What you are training
Every melody has a shape, and the shape carries meaning before a single word is heard. An arch rises and returns, which feels complete; a rising ramp builds and demands release; a wave rocks in place, which is how verses stay conversational; a falling line settles. Choruses tend to sit higher and move less; verses move more and sit lower. Writers who think in contour write melodies that mean what the lyric means, and they fix a flat section by changing its shape rather than adding notes. This drill plays a short phrase and asks you to identify its contour, then shows the shape drawn against the notes. A few rounds teach you to hear the arc of your own melodies, which is usually the first thing to fix when a chorus feels like a second verse.
After this drill, the plan: The daily plan follows contour with melody writing: you get a lyric and a shape and write the phrase that fits both.