UML is part of it. We use Visio, iRise and other tools for all sorts of graphic representations of requirements.
Everyone is a visual learner. It’s how human beings work. When people can easily visualize a solution they know when they have found it.
Visio I've been using since waaaaaaay back before Microsoft owned it .. iRise is something new I'm going to have to go look up, thanks for that! :-)