I could define workflow  for you :
The automation of a business process, in whole or part, during which
documents, information or tasks are passed from one participant to
another for action, according to a set of procedural rules.
and workflow engines can now handle very complex series of
processes.

As a view of 3000 feet I can say that it manages states of an object for example : employment of personnel may have diffrent situation such as "in test period" and "formal" , .... , changing an objects' state has its own roles which are managed by engine.

i continue the question  for more in depth .
could a workflow  engine use with spring frame work ?
as we know , spring manage evry thing for us, from bean managment to
database , tranction and ... that each part can done with seperate
framework but manage all framework by spring (for example use
hibernate for OR mapping but we deffine hibernate in spring to manage
it ).

i know (or think) that workflow engine  is not design for manage
resources but design for write your logical scenario of executing of
bussiness flow .

in this situation if a workflow engine can use it with spring ?
or is a workflow enging do managing the resource and actions as power
as spring ?

http://www.opensymphony.com/osworkflow/2.3%20Spring%20framework.html
http://wiki.opensymphony.com/display/WF/2.3+Spring+framework

If you wanna manage your workflows by spring notice and attention to this link :
www.javaworld.com/.../jw-0411-spring.html

But if you wanna manage your workflows by workflow  engin you could use thses articles :

1- JBPM (JBoss) (Recommended)
2- ActiveBPEL
3- Flux 6.5

also taking a short look at this site:

http://is.tm.tue.nl/research/patterns/

there is a person named bartek his PHD thesis is on workflow, an small PDF file, if you read this you will get lots of information about what is wrong and what is good about most workflow  engines.

A workflow  engine tries to take out the definition of a process from inside the code. This process definition will be usually explained in a specific format and language other than the original source code. Examples are XML for JBPM.
This way the users of the system can change the process ( Flow of execution inside the system) without any need to re-compile or changing any code. As a result the system will become a lot more flexible.

Two major applications for workflow engines are internal and external. Internal workflow engines are used inside one program to control the flow of execution of the processes in it and external engines usually control the flow of a process between multiple systems.. a lot of these systems today are Web Services and this is the base for Service Orchestration and part of SOA.

Well these are just some points about workflow engines, I am sure everybody here will help with better information.

These links have good information about this topic:

www.theserverside.com/.../article.tss?l=Workflow
http://www.e-workflow.org/

See also the Imixs Workflow Project. Imixs Workflow is the open source BPM technology to build modern business applications even faster and flexible.
http://www.imixs.org