Using workflow rules for specific layouts.
Workflow rules are created for a specific module. You can create a workflow rule for the Deals module to automate the process of following-up on a big deals and creating timely tasks for the team. That is neat but say for example, a company sells furniture and also refurnishes homes. They sell goods and provide services as well and so their business process is different in each case.
In this scenario, using page layouts, they can create two layouts for Leads, Deals, etc. One layout that captures the information for selling goods and the other that stores details on the service requests. One layout will have information on the estimated date of delivery which needs to be updated if the stocks are available. Another will have details on the estimated date of completing the project, based on which you may assign tasks to your team. In short, both follow a different set of process.
To automate the process, you can create separate workflow rules for the same module but specifying a different layout to address the requirements for each process.
Here is the tip. While creating the workflow rule, specify the layout as an additional criteria. That way, workflow rules will be executed for records that meet the criteria and come under the specified layout.
Here is a link to additional scenarios to help you understand how workflow rules and layouts work together.