You can use plain text for everything. Writing technical documentation and prose, keeping notes and making plans. Usually I type my words into Vim, but today I'm composing this page in TextEdit.app.
Why? TextEdit is the best way of introducing plain text to people who just started learning or to those who only touch their computer occasionally.
Word Processors. Microsoft Word, Pages.app, OpenOffice, and similar apps are suitable for creating printable documents and printing them on paper, but not for editing text. These excellent pieces of software distract you from writing words. You rarely use any of their features, but they slow you down.
Cloud Services. Google Docs, Evernote, Notes.app, etc. Cloud services are beautiful and convenient, but the sad truth is that there is no cloud --- it's just someone else's computer. Do you trust those corporations? You should not. They can accidentally block your account or lose your data, and you will rarely get prompt support --- if you get any support --- in these situations. And what if they shut the service down? Can you transfer your data out? Is the data format portable --- can you open your files in another app? Can you use the cloud when you are offline? If yes, does it reliably sync your devices? Can you make backups and validate them? How easy is it to restore?
Text Editors. When you are learning to program or just making quick text edits, use TextEdit. As soon as you get serious about programming or writing, you can switch to powerful text editors like Vim or Emacs.
The plain text file format is straightforward and portable. You can open and edit your plain text files on any computer or phone. All operating systems support plain text natively and will always support it. You can edit your files with any text editor --- no need to convert, import or export anything. It just works. Everywhere.
Plain text files are small and easy to manage. Plain text tools are powerful. With plain text you get superpowers of version control, rendering to printable documents and web pages, and simple backup, restore, and encryption.
TextEdit.app is pre-installed on every Mac and supports plain text. It is fast, simple, and beginner-friendly. Learn it once, use it for years. You get auto save and versions for free. TextEdit has everything you need and has nothing else.
To start using it for plain text files, set these defaults.
Note: You can also adjust the default font and size by clicking on Change beside Plain text font.
You can always adjust the font size in the current window with ⌘+ and ⌘-.
Optionally, go to Preferences > Open and Save. Check When Opening a File to Display HTML files as HTML code instead of formatted text.
Now you can close the TextEdit window and open a new one in plain text.
You can write some prose in TextEdit, but editing long texts, especially across multiple files, is inefficient. To be honest, I switched to Vim to edit this page as soon as the first draft was complete.
Plain text is awesome!
Tested on macOS 10.13.