Is the starting point. It explains what the workflow package does and
provides the knowledge necessary to formalize workflow processes using
this package.
A guide for those formally defining a workflow process. This is
necessary to do in order to take advantage of the workflow
package. This is for building advanced workflows where you'll need
(and want) know how the engine operates.
The other one was a guide, this is the reference. Is for the readers
already familiar with the concepts, but who wishes to quickly look up
a specific term. It's organized alphabetically and conceptually,
instead of pedagogically.