We’ve finally made it to the most intimidating of Eloquent relationships: many to many polymorphic. Don’t worry; it’s far simpler to understand than you might initially think. In this lesson, we’ll construct a standard many-to-many relationship: a user can "like" a post. Then, we’ll throw a wrench into the mix. What if a user can also "like" a comment? How might we restructure our existing structure to allow for this?
via Laracasts
Many to Many Polymorphic Relations