->> is a function at the type level without extra properties like matchability, so it can be simply read as "to" or "into" -> is used with type constructors li

->> is a function at the type level without extra properties like matchability, so it can be simply read as "to" or "into" -> is used with type constructors like Maybe or Either, and arguments passed to it can still be "read" in the result (for example, a -> Maybe a, or a -> b -> Either a b). I would call it a "slotting" arrow to connote that the argument will be fitted into a hole of a type constructor. So I would read a -> Maybe a as "slotting a into Maybe".