It's called ~. If you mark it as hidden on Windows, it will be completely invisible even if you enable hidden files in the explorer (unless you also force it to show protected system files), because a name starting with a tilde has a special meaning. On Linux you'll have to handle me with care (just like IRL), with cd '~'.

It contains a lot of lists, spreadsheets, databases, to handle a notebook stash, a pen stash, many unfulfilled dreams, unfinished projects, an overwhelming amount of chores to do, many ideas that will never come to fruition, and there are completely unreadable scripts in cursed programming languages to make RSS feeds out of this. And of course in the middle of this whole mess, there's a list of all the lists, which contains itself. There are also are a whole bunch of love letters addressed to you, but if you open any of them, something runs to take a picture of you from your camera just to record you blushing.