Flowcharts, data flow diagrams, workflows, process diagrams, activity diagrams, process maps: No matter what you call them, you have most likely used them! Flow charts are the most common diagram type that is used in all industries and across all departments to clearly visualize the steps in any process.
They can be used to plan new processes, optimize existing processes, document software programs in development, explain processes simply to onboard new team members, plan project milestones, and more. Flowcharts are also commonly used as checklists, and may be audited to ensure a company is following their documented processes reliably for certification requirements (ISO, SOX, etc.)
Some departments may use specialized types of process diagrams, like BPMN diagrams or UML activity diagrams. But most people use easily recognizable shapes and simple rules to create their flowcharts.
Flowcharts use basic shapes like rectangles, diamonds and circles to indicate the different steps, interactions and decisions in a process, linked together with arrows (connectors) to show the direction between steps. More complex procedures may be split over multiple pages.