For as long as people have been traveling from point A to point B, they've relied on maps to help them find their way. Workflow diagrams (also called flowcharts) fulfill a similar function, detailing every step that a process takes, including dependencies, responsibilities, and tools. This allows users to logically plot out effective workflows, eliminate inefficient steps and blockers, collaborate among teams, and see possible next steps at every stage of a project.
For an example of a workflow design tool that uses workflow diagrams, see ServiceNow Flow Designer. Flow Designer enables both professional developers and low-code business analysts to automate and integrate any business process as a digital workflow using natural language.
Activity diagrams take this concept further; an activity diagram is a Unified Modeling Language (UML) behavior diagram that represents the workflow of activities within a system, using formally specified notation, symbols, and rules. An Activity Diagram in UML is generally used in modeling software systems; they are considered behavioral diagrams, because they describe what must happen in the systems, they are modeling.