Org is theoretically just a markdown format. In practice it starts out as a markdown editor with a bunch of neat features, and can become this omnibus of organization. There's a whole organizational ecosystem which uses org as a sort of lingua franca, so the more you sacrifice at its alter the more it all comes together. I use it to unify my todo list and calendar, and have it display what needs to happen both on an hour to hour level and day to day. I use it to pin emails I want to reply to with one key combo, and connect notes to each other any way I want. I have no idea if it's useful enough to justify the time I put into it. For most people, probably not. But I've gotten it to the point that it's just totally frictionless for me, and not a single other system I've ever used has been easy enough to stick to.