Deep holds two values: a value (often a functor) in deep, and another Algae.Free.t in deeper

A simple wrapper for some data. This can be seen as a prototypical ADT

Kleisli helps to define Kleisli categories (and monadic arrows). The objects of this category are members of an underlying type, and the arrows between them. The arrows have an actual type of X -> T(Y), but by the nature of the category, are thought of as simply X -> Y