This will make a lot more sense with a little bit of dialogue. and also with more detailed images. Basically, the taller of the two brothers is longwindedly explaining his tale, which we see as images in his speech bubbles, along with a bit of narration. There are no panel borders up here, both to get the sense that the tale is all sort of running together and to show the the taller brother is talking in a more or less nonstop stream of conciousness.
The gist of what's happening is that the tall one is making a snack, he gets a letter that tells him he needs go go save the world, and then he sets out to do so. with minor wackiness along the way.
Down along the bottom we have both characters in deep conversation. The storyteller is gestulating wildly and basically acting out parts of his story, while the other brother slowly falls asleep.