Songwriting is constructing the actual Song as opposed to just writing the verses.
It deals with matching the lyrics to a concept, constructing an effective hook, adding bridges if it need be, making sure their is a smooth transition from the verse to the hook, creating a fully realized concept that matches the instrumental, etc
Writing verses is just a small part of songwriting and probably the easiest.
Lots of rappers can write killer verses but 99% of them couldn't write a song to save their life.
Jadakiss, Freddie Gibbs (outside some songs), Pusha T, they all can write killer verses anytime they want. But, their careers have all suffered because they have difficulty writing great singles.
It is precisely in this area that Drake excels as an artist.
Drake and his team can even flip an already great pop song...
...into an even bigger pop song.
And he does this consistently. Throughout all of his major releases.
That's why he's going to be tough to dethrone...
but, it's starting already...
WATTBA was the first release by him that had some truelly sloppy songwriting.