org-mode is a markdown like language. In itself it doesn't have anything special. But the ecosystem of integration in emacs makes it a very rich experience. Both the UX of integration (seemless idea capture, outline manipulations etc.) and the breadth of application (email writing, gantt generation, accounting compute and reporting, RSS reading and sorting, slide presentations, agenda integration, time card reporting, invoice generation etc.) in combination it becomes a very hard to describe experience, precisely because it is so rich and varied while at the same time very streamlined because everything is text, and it all behave intuitively.