I don’t know anyone who doesn’t take notes. Most of the people I know use an online note-taking application like Evernote, Simplenote, or Google Keep.
All of those are good tools, but they’re proprietary. And you have to wonder about the privacy of your information—especially in light of Evernote’s great privacy flip-flop of 2016. If you want more control over your notes and your data, you need to turn to an open source tool—preferably one that you can host yourself.