Workflows allow you to have multi-staged deployments of cloud resources. A workflow is made up of one or more stages. Each stage is made up of actions to create, update, replace, or delete cloud resources. If you have more than one stage you can connect them using a transition. A transition allows a workflow to prompt the user on what action to take next.
Workflows allow you to have more control over how cloud resources are replaced. Typically when you make a change to a cloud resource that requires it to be replaced your only options are to delete the resource, then create a new one, or create a new one and delete the old one. This model of deployment runs the risk of causing outages. With workflows you get more fine grained control over how cloud resources are replaced.