TokenMismatchException

I'm following this tutorial - https://laracasts.com/series/laravel-5-from-scratch/episodes/9 . Here at around 11:00 we're supposed to create a new note... and after following everything as showed, and cross checking it for almost an hour i don't know WHY i was getting a "TokenMismatchException" .. whose solution was to add "" to my form (which i found on laracasts user comments) .

Is there a specific reason why this was not mentioned in the tutorial?