Enum members are sequentially ordered types — they can be enumerated. The main advantage of the Enum typeclass is that we can use its types in list ranges. They also have defined successors and predecessors, which you can get with the succ and pred functions.

Scalaz equivalent for the Enum typeclass is Enum:

scala> 'a' to 'e'
res30: scala.collection.immutable.NumericRange.Inclusive[Char] = NumericRange(a, b, c, d, e)

scala> 'a' |-> 'e'
res31: List[Char] = List(a, b, c, d, e)

scala> 3 |=> 5
res32: scalaz.EphemeralStream[Int] = scalaz.EphemeralStreamFunctions$$anon$4@6a61c7b6

scala> 'B'.succ
res33: Char = C

Instead of the standard to, Enum enables |-> that returns a List by declaring pred and succ method on top of Order typeclass. There are a bunch of other operations it enables like -+-, ---, from, fromStep, pred, predx, succ, succx, |-->, |->, |==>, and |=>. It seems like these are all about stepping forward or backward, and returning ranges.