Workflows are automated business processes that consist of Steps and Actions. A Workflow is an asynchronous processes; it doesn't require user input data. A Workflow can be triggered by an event (automated Workflow) or by a user (manual Workflow).
Note
Microsoft Dynamics CRM 2011 On-premises also supports custom Workflow Activities (like CRM 4.0) and custom XAML Workflows. An XAML Workflow can be visually designed and created in Visual Studio Workflow Designer, without coding.
There are some major differences between Workflows and Plug-ins:
Workflows run asynchronously in the background. Plug-ins can run both asynchronously and synchronously.
Workflows can be triggered manually (security context of the user who trigged it), or automatically (security context of the workflow owner) by selected events. Plug-ins can only be trigged by the message (security context of the CRM Web application pool identity) for which they're registered.
Workflows provide the flexibility...