It looks like a whiteboard to me? But my vision can be iffy so I may be wrong. It just appears to be a starker white in the area with the scribbles than the rest of the wall.
My best guesses:
1. To-do lists that will never be completed.
2. Grocery lists that may actually be completed.
3. Corny, Facebook-mom-esque inspirational/lovey-dovey quotes Gin and Jen write back and forth to each other. This guess is because the words appear to be in sentence/paragraph form rather than typical lists. Also I think I see either an emoji or poorly drawn quotation marks in black marker.