Arguably the most successful platform whose code can be easily modified at runtime. Emacs presents this through the metaphor of a text editor, though the Emacs platform has been about more than that since pretty much its inception. Emacs as a platform hosts email readers, Usenet clients, web and Gopher browsers, games, terminal emulators, sftp clients, chat clients, and even a window manager. With org-mode, most of these (including the email clients) can be linked together with agendas, task lists, and personal notes to form an integrated tracking system. org-roam extends this yet further.
As a text editor, it is remarkably proficient, with specialist features for dozens of programming languages and support for both Emacs and vim-style keybindings.
I believe it is a mistake to regard Emacs as simply a text editor.
The Emacs Wiki is also great.
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Old technology is any tech that’s, well… old.
According to its website, org-roam is “a plain-text personal knowledge management system”. It is based on the popular Zettelkasten knowledge management system, or the Roam Research website. But because it layers atop org-mode and therefore Emacs, it has a lot of power that the others lack; for instance, integration with email and agendas.
org-mode is a toolkit for you to organize things. It is part of Emacs.