Incorprate @grayjay's comment improvement suggestions

Author: erikd

cabal-install-solver/src/Distribution/Solver/Types/SummarizedMessage.hs

@@ -15,11 +15,17 @@ import Distribution.Solver.Modular.Dependency
     ( ConflictSet, QGoalReason, GoalReason )
 import qualified Distribution.Solver.Modular.ConflictSet as CS
 
--- The following types are used to encode results from the dependency
--- solver so they cab be easily displayed in the module
+-- The following types are used to encode log messages from the
+-- dependency solver so they can be easily displayed in the module
 -- `Distribution.Solver.Modular.Message`.
+--
+--  These types are an intermediate representation of the solver log.
+-- The log is converted from a list of Message to a list of
+-- SummarizedMessage to a list of String. Message is very similar to
+-- the structure of the search tree but difficult to read, and
+-- SummarizedMessage has the structure that is shown to users.
 
--- Encoding of solver results.
+-- Encoding of solver messages.
 data Entry
   = EntryPackageGoal QPN QGoalReason
   | EntryRejectF QFN Bool ConflictSet FailReason