Visual Workflow is a tool that allows you to create flows that automate business processes in Salesforce.
Flows consist of elements that define the logic, data manipulation, and user interface of the flow. Elements can be used to pass data to legacy systems using outbound messages or Apex actions, update fields in the database using record elements, and perform other tasks. Only one version of a flow can be activated at a time, meaning that only one version can run when triggered by users or processes. Verified References:
[Salesforce Help: Visual Workflow]