I'm surprised there's only one other person in this discussion who has mentioned swim lanes. They are incredibly useful!
Swimlanes are basically process flow diagrams (aka flow charts) but with lanes that indicate which actor or system performs each process.
At my company, if an engineer gets tasked with a logically complex feature or a feature that involves multiple different systems, then we will often require them to use swimlanes to diagram out their new feature before they start coding it. The flow chart makes it easier for the business owner to double check the logic before it's implemented. The lanes help the engineer better understand more intuitive ways to organize their code (classes, methods, etc) and the interactions it will create. Without the lanes, code organization on logically complex features involving multiple actors can go off the rails pretty quickly.
Swimlanes are basically process flow diagrams (aka flow charts) but with lanes that indicate which actor or system performs each process.
At my company, if an engineer gets tasked with a logically complex feature or a feature that involves multiple different systems, then we will often require them to use swimlanes to diagram out their new feature before they start coding it. The flow chart makes it easier for the business owner to double check the logic before it's implemented. The lanes help the engineer better understand more intuitive ways to organize their code (classes, methods, etc) and the interactions it will create. Without the lanes, code organization on logically complex features involving multiple actors can go off the rails pretty quickly.
For database table specs we use ERDs.