Elmo and cookie monster both love cookies. Elmo is the only one with cookies. Due to an unfortunate situation Elmo's cookies get stolen and now he does not have enough cookies to share. Cookie Monster still wants cookies but Elmo does not have enough to share. Elmo decides to split his cookie and share with Cookie Monster.
Robin explains the sharing economy to the rest of the Teen Titans, as they are unfamiliar with it. He makes sure to show how much money he made through his participation, which entices the other Titans to join. Robin then demonstrates how to participate in the sharing economy: using a smartphone application. Cyborg uses the app to rent out his left arm to Beast Boy.
In this scene, Elmo meets his friend, who has has milk while Elmo has cookies. Elmo would like some milk to enjoy with his cookies, and Elmo's friend would like some cookies to enjoy with her milk. To solve this conflict they both decide to share their cookies and milk together.