Difference between Workflow and Plug-in

In Microsoft Dynamics CRM 2011, workflows are now called processes. In addition to this change, there are two categories of processes:

• Workflows. The automated or asynchronous processes that may require user input to start them. Further, these processes do not require user input to run them to completion. These processes run in the background.
  
• Dialogs. The interactive or synchronous processes that require user input to start and run them to completion. When you start the dialog process, a wizard-like interface is presented to you so you can make appropriate selections to run the process.